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Bypassing the XSS Filters : Advanced XSS Tutorials for Web application Pen Testing

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<span style="color: red;">Bypassing the XSS Filters :<br />Advanced XSS Tutorials for Web application Pen Testing</span></h2>
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Hi friends, last time, i explained what is XSS and how an attacker can inject malicious script in your site. As i promised earlier, i am writing this advanced XSS tutorial for you(still more articles will come)</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxNgeVIGlsWmiE8xEw-wLpGaWS6kY52c2gnz-d-_aQyKqx16VCbLh6JmvBBo9_uS3ZvaRysdSyIrv4wMd-J37eidLau4rCU8L0jPpYXa_SyzCjXwakPO8Ax6OBSYlU8D8O8HpasR8-oXWr/s1600/XSS+Vulnerability+Tutorial+BreakTheSec.png" imageanchor="1" style="color: #888888; text-decoration: none;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxNgeVIGlsWmiE8xEw-wLpGaWS6kY52c2gnz-d-_aQyKqx16VCbLh6JmvBBo9_uS3ZvaRysdSyIrv4wMd-J37eidLau4rCU8L0jPpYXa_SyzCjXwakPO8Ax6OBSYlU8D8O8HpasR8-oXWr/s1600/XSS+Vulnerability+Tutorial+BreakTheSec.png" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" /></a></div>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">.</span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Sometimes, website owner use XSS filters(WAF) to protect against XSS vulnerability.</span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For eg: if you put the <scirpt>alert("hi")</scirpt></span></div>
, the Filter will <span class="IL_AD" id="IL_AD5" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">escape</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"> the "(quote) character , so the script will become</span><br />
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<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
<script>alert(>xss detected<)</script></blockquote>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Now this script won't work. Likewise Filters use different type of filtering method to give protection against the XSS.  In this case, we can use some tricks to bypass the filter.  Here i am going to cover that only. </span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
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1.Bypassing magic_quotes_gpc</h2>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">The magic_quotes_gpc=ON is a PHP setting(configured in PHP.ini File) , it </span><span class="IL_AD" id="IL_AD4" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">escapes</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">the every ' (single-quote), " (double quote) and \  with a backslash automatically.</span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For Eg:</span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"><scirpt>alert("hi");</scirpt></span> will be filtered as <script>alert(\hi\)</script>.so the script won't work now.<br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">This is well known filtering method, but we can easily bypass this filter by using ASCII characters instead.</span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For Eg:  alert("hi"); can be converted to</span><br />
<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
String.fromCharCode(97, 108, 101, 114, 116, 40, 34, 104, 105, 34, 41, 59)</blockquote>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">so the script will become <script>String.fromCharCode(97, 108, 101, 114, 116, 40, 34, 104, 105, 34, 41, 59)</script>.  In this case there is no "(quotes) or '(single quotes) or / so the filter can't filter this thing.  Yes, it will successfully run the script.</span><br />
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String.fromCharCode() is a javascript function that converts ASCII value to Characters.</div>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<b style="background-color: white; color: #274e13; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">How to convert to ASCII values?</b><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">There are some online sites that converts to ASCII character. But i suggest you to use</span><a href="https://addons.mozilla.org/en-US/firefox/addon/hackbar/" style="background-color: white; color: #888888; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; text-decoration: none;">Hackbar Mozilla addon </a><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">.</span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">After installing hackbar add on ,press F9.  It will open the small box above the url bar. click the XSS->String.fromCharCode()</span><br />
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<a href="http://1.bp.blogspot.com/-HOO_mqpXuys/TvdV-D5KW2I/AAAAAAAABHs/QHEmx1FBjgY/s1600/XSS+breaking+security.jpg" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" src="http://1.bp.blogspot.com/-HOO_mqpXuys/TvdV-D5KW2I/AAAAAAAABHs/QHEmx1FBjgY/s1600/XSS+breaking+security.jpg" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" /></a></div>
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<a href="http://4.bp.blogspot.com/-JqB82lpCwjQ/TvdV_l4bE7I/AAAAAAAABH0/21POwKEv2jc/s1600/XSS+bypassing+filters.jpg" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" src="http://4.bp.blogspot.com/-JqB82lpCwjQ/TvdV_l4bE7I/AAAAAAAABH0/21POwKEv2jc/s1600/XSS+bypassing+filters.jpg" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" /></a></div>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Now it will popup small window. enter </span><span class="IL_AD" id="IL_AD6" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">the code</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">for instance alert("Hi").  click ok button.  Now we got the output.</span><br />
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<a href="http://3.bp.blogspot.com/-9tuNcvwOvx4/TvdV7zrQlwI/AAAAAAAABHk/uzUWnsyk5ls/s1600/xss+advanced+tutorial.jpg" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" src="http://3.bp.blogspot.com/-9tuNcvwOvx4/TvdV7zrQlwI/AAAAAAAABHk/uzUWnsyk5ls/s1600/xss+advanced+tutorial.jpg" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" /></a></div>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">copy the code into the <script></script> inside and insert in the vulnerable sites</span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<i style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For eg: </i><br />
<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
hxxp://vulnerable-site/search?q=<script>String.fromCharCode(97, 108, 101, 114, 116, 40, 34, 104, 105, 34, 41, 59)</script></blockquote>
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<h2 style="background-color: white; color: #274e13; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 11px; font-stretch: normal; margin: 0px 0px 1em; position: relative;">
2.HEX Encoding</h2>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">we can encode our whole script into HEX code so that it can't be filtered. </span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For example:  <script>alert("Hi");</script> can be convert to HEX as:</span><br />
<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
%3c%73%63%72%69%70%74%3e%61%6c%65%72%74%28%22%48%69%22%29%3b%3c%2f%73%63%72%69%70%74%3e</blockquote>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Now put the code in the vulnerable site request.</span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For ex: </span><br />
<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
hxxp://vulnerable-site/search?q=%3c%73%63%72%69%70%74%3e%61%6c%65%72%74%28%22%48%69%22%29%3b%3c%2f%73%63%72%69%70%74%3e</blockquote>
<b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"> Converting to HEX:</b><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">This site will convert to hex code: http://centricle.com/tools/ascii-hex/ </span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<h2 style="background-color: white; color: #990000; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 11px; font-stretch: normal; margin: 0px 0px 1em; position: relative;">
3.Bypassing using Obfuscation</h2>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Some website admin put the </span><i style="background-color: white; color: #cc0000; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">script</i><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">,</span><i style="background-color: white; color: #cc0000; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">alert</i><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"> in restricted word list.  so whenever you input this</span><span class="IL_AD" id="IL_AD3" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">keywords</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">, the filter will remove it and will give error message like "you are not allowed to search this". This can bypassed by changing the case of the keywords(namely Obfuscation). </span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For eg:</span><br />
<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
<script>ALeRt("hi");</script></blockquote>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">This bypass technique rarely works but giving trial is worth. </span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<h2 style="background-color: white; color: #38761d; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 11px; font-stretch: normal; margin: 0px 0px 1em; position: relative;">
4. Closing Tag</h2>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Sometimes putting "> at the beginning of the code will work. </span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
"><script>alert("Hi");</script></blockquote>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">This will end the previous opened tag and open our script tag.</span><br />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Example:</span><br />
<blockquote class="tr_bq" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
hxxp://vulnerable-site/search?q="><script>alert("Hi");</script></blockquote>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<div style="background-color: white; color: #990000; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
<b>Conclusion:</b></div>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">From above article, it is clear that XSS filters alone not going to protect a site from the XSS attacks. If you really want to make your site more secure, then ask PenTesters to test </span><span class="IL_AD" id="IL_AD8" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">your application</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"> or test yourself.</span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Also there are lot of different filter bypassing technique, i just covered some useful techniques for you.</span><br />
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" />
<div style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">
<b><span class="Apple-style-span" style="color: #cc0000;">Disclaimer:</span></b></div>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">This article is intended for educational purpose only.</span></div>

Bypassing the XSS Filters : Advanced XSS Tutorials for Web application Pen Testing

Bypassing the XSS Filters : Advanced XSS Tutorials for Web application Pen Testing Hi friends, last time, i explained what is XSS and...

+ Read more »

What is XSS (Cross Site Scripting)

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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4O3b3Jnto6A_4gEkMBw2Th0gH8D6BGjzWHxIhOn_CNp40pvvSTsdPP3ibW2yMHWh6XhsFZ_WOkNu4QvS4wyjupGEOJXV_yVt_uB3AOaiOo-PHNAyEY2R16O8TPB9O8K-FHU693YZIRINI/s640/cross-site-scripting-xss.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4O3b3Jnto6A_4gEkMBw2Th0gH8D6BGjzWHxIhOn_CNp40pvvSTsdPP3ibW2yMHWh6XhsFZ_WOkNu4QvS4wyjupGEOJXV_yVt_uB3AOaiOo-PHNAyEY2R16O8TPB9O8K-FHU693YZIRINI/s640/cross-site-scripting-xss.png" /></a></div>
<br />
<b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"><span class="Apple-style-span" style="color: #38761d;">What is XSS?</span></b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Cross Site Scripting also known as XSS , is one of the most common web appliction vulnerability that allows an attacker to run his own client side scripts(especially Javascript) into web pages viewed by other users.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">In a typical XSS attack, a hacker inject his malicious javascript code in the legitimate website . When a user visit the specially-crafted link , it will execute the malicious javascript. A successfully exploited XSS vulnerability will allow attackers to do phishing attacks, steal accounts and even worms. </span><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"> </b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Example :</b><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Let us imagine, a hacker has discovered XSS vulnerability in Gmail and inject malicious script. When a user visit the site, it will execute the malicious script. The malicious code can be used to redirect users to fake gmail page or capture cookies. Using this stolen cookies, he can login into your account and </span><span class="IL_AD" id="IL_AD9" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">change password</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">.It will be easy to understand XSS , if you have the following prerequisite:</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br />
<ul style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 1.4; margin: 0.5em 0px; padding: 0px 2.5em;">
<li style="margin: 0px 0px 0.25em; padding: 0px;">Strong Knowledge in HTML,javascript(<a href="http://w3schools.com/" rel="nofollow" style="color: #888888; text-decoration: none;">Reference</a>).</li>
<li style="margin: 0px 0px 0.25em; padding: 0px;">Basic Knowledge in HTTP client-Server Architecure(<a href="http://101.lv/learn/CGIperl/ch2.htm" rel="nofollow" style="color: #888888; text-decoration: none;">Reference</a>)</li>
<li style="margin: 0px 0px 0.25em; padding: 0px;">[optional]Basic Knowledge about server side programming(php,asp,jsp)</li>
</ul>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span class="Apple-style-span" style="background-color: white; color: #38761d; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 19px; font-weight: bold;">XSS Attack:</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Step 1: Finding Vulnerable Website</b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Hackers use google dork for finding the vulnerable sites for instance  "?search=" or ".php?q=" .  1337 target specific sites instead of using google search.  If you are going to test your own site, you have to check every page in your site for the vulnerability. </span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Step 2: Testing the Vulnerability:</b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">First of all, we have to find a input field so that we can inject our own script, for example: search box, username,password or any other input fields.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEja0byma54fJGG8idnecwhP3aQyz0C1LbQtS9c0tZTnjeM0EuIM5FuUXqVr18E1M45Di6d-uOIWawyOeYMJ6Ruat0FrY-KAD-cQMfkDQo79i8KENm4rPJFvqxtEIHUo0vPISVL76Mmp0u8/s1600/search+box.jpg" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEja0byma54fJGG8idnecwhP3aQyz0C1LbQtS9c0tZTnjeM0EuIM5FuUXqVr18E1M45Di6d-uOIWawyOeYMJ6Ruat0FrY-KAD-cQMfkDQo79i8KENm4rPJFvqxtEIHUo0vPISVL76Mmp0u8/s1600/search+box.jpg" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" /></a></div>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"><i>Test 1 :</i></b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Once we found the input field, let us try to put some string inside the field, for instance let me input "BTS". It will display the  result .</span><br />
<div class="separator" style="background-color: white; clear: both; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXngL1NRorBv-7FFzAe_6YQIJ5OrpfrzWb2A-iuTILw-rDQdvEP1u2r5Cd6KQQ0c-ojMRFWab4s8DVUI_2W7xONdsLT_XMEj1r7elWDLP6O7o6Sc-f3dIjj-Z9S9ci3H9tjwm2vI_s9nw/s1600/XSS_input.gif" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXngL1NRorBv-7FFzAe_6YQIJ5OrpfrzWb2A-iuTILw-rDQdvEP1u2r5Cd6KQQ0c-ojMRFWab4s8DVUI_2W7xONdsLT_XMEj1r7elWDLP6O7o6Sc-f3dIjj-Z9S9ci3H9tjwm2vI_s9nw/s1600/XSS_input.gif" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" width="200" /></a></div>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Now right click on the page and select view source.   search for the string "BTS" which we entered in the input field.  Note the location where the input is placed.</span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbg96oYtcvtFTAcXIl6eM8MuBszgLYKwDlR-r5E632GgaVlB3F74hZ24ZqDyQqwcAcfYdhbQDrLz5sEpYFHiYTiORfgqKFkCt0iBaO0b7lWZeaElEZ144wMV-m_q6WELRNK4YGWufXqFk/s1600/BTS_XSS.gif" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" height="69" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbg96oYtcvtFTAcXIl6eM8MuBszgLYKwDlR-r5E632GgaVlB3F74hZ24ZqDyQqwcAcfYdhbQDrLz5sEpYFHiYTiORfgqKFkCt0iBaO0b7lWZeaElEZ144wMV-m_q6WELRNK4YGWufXqFk/s1600/BTS_XSS.gif" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" width="200" /></a></div>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"><i>Test 2:</i></b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Now we are going to check whether the server sanitize our input or not.  In order to do this , let us input the <script> tag inside the input field. </span><br style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"></p>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjO4bnV0_W6J1gbexCQ1QquWobSZAilA1swX9lI5X_A-mJs0QoIGIwk-ERVldwiRvrBVoAAwXvChZlkRL8ZzZXSuiNU4jDgy6sGG-zOVCHsFAGVWa-P-wCvjFoBd_DqRU6H4c8KVAXnKvc/s1600/Xss_script_tag.gif" style="text-decoration: none; color: rgb(136, 136, 136); margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjO4bnV0_W6J1gbexCQ1QquWobSZAilA1swX9lI5X_A-mJs0QoIGIwk-ERVldwiRvrBVoAAwXvChZlkRL8ZzZXSuiNU4jDgy6sGG-zOVCHsFAGVWa-P-wCvjFoBd_DqRU6H4c8KVAXnKvc/s1600/Xss_script_tag.gif" width="200" style="border: 1px solid rgb(238, 238, 238); position: relative; padding: 5px; -webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></a></div>
<p>
<span style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);">View the source of the page . Find the location where input displayed place in previous test.</span><br style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"></p>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBZC118gbOJ-dnrWSPPLxOWm2zOSkwvn9s4vG8zm5uCXYD0tFYS4hsdTbyb-rtmwBUhBr5cbJvR_yywLEXfWIxgMs7IwIgDzfG-pZOSCa23vxB1-9yh3hyOpK0NQSdv-8anrVpDHh9C7A/s1600/xss-SUCCESS_Noparsing.gif" style="text-decoration: none; color: rgb(136, 136, 136); margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBZC118gbOJ-dnrWSPPLxOWm2zOSkwvn9s4vG8zm5uCXYD0tFYS4hsdTbyb-rtmwBUhBr5cbJvR_yywLEXfWIxgMs7IwIgDzfG-pZOSCa23vxB1-9yh3hyOpK0NQSdv-8anrVpDHh9C7A/s1600/xss-SUCCESS_Noparsing.gif" width="250" style="border: 1px solid rgb(238, 238, 238); position: relative; padding: 5px; -webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; background-image: initial; background-attachment: initial; background-size: initial; background-origin: initial; background-clip: initial; background-position: initial; background-repeat: initial;"></a></div>
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<br style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"><span style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);">Thank god, our code is not being sanitized by the server and </span><span class="IL_AD" id="IL_AD6" style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);">the code</span><span style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"> is just same as what we entered in the field. If the server sanitize our input, the code may look like this </span><i style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"><span class="Apple-style-span" style="color: rgb(153, 0, 0);"><script></span></i><span style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);">. This indicates that the website vulnerable to XSS attack and we can execute our own scripts .</span><br style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"><br style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"><b style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"><span class="Apple-style-span" style="color: rgb(204, 0, 0);">Step 3: Exploiting the vulnerability</span></b><br style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);"><span style="color: rgb(102, 102, 102); font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; background-color: rgb(255, 255, 255);">Now we know the site is somewhat vulnerable to XSS attack.  But let us make sure whether the site is completely vulnerable to this attack by injecting a full javascript code.  For instance, let us input <script>alert('BTS')</script> .</span><br />
<div class="separator" style="background-color: white; clear: both; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUXdanup-U2NimSaHps0wS8zDCuNy6vNY2u0lR8CPr16c_hroyScgMNFuxZeIXEgFj1ADB_tXksA8wI2xRSuTUe24_lN3kETfQE6wKx7Ma2sSxonsgFuLTrI5XSQHmgUo9LrgUo17FEaM/s1600/injecting-XSS.gif" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" height="31" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUXdanup-U2NimSaHps0wS8zDCuNy6vNY2u0lR8CPr16c_hroyScgMNFuxZeIXEgFj1ADB_tXksA8wI2xRSuTUe24_lN3kETfQE6wKx7Ma2sSxonsgFuLTrI5XSQHmgUo9LrgUo17FEaM/s200/injecting-XSS.gif" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" width="200" /></a></div>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Now it will display pop-up box with 'BTS' string. Finally, we successfully exploit the XSS .  By extending the code with malicious script, a hacker can do steal cookies or deface the site and more.</span><br />
<div class="separator" style="background-color: white; clear: both; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBJY2PNEIUDVKvtgjXzwJ99m_jaV2zSMNwe3rz4GD0lO7tV-eI2nMTuYz-TWDwClXctB5e_0ryqIAFzfUMEdXMX6dvkt4fd4fsGYuTCpnrjX_P3uLVjQYmRbAQdD55jcKE3TYzch8Biko/s1600/alert-box-xss.gif" style="color: #888888; margin-left: 1em; margin-right: 1em; text-decoration: none;"><img border="0" height="118" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBJY2PNEIUDVKvtgjXzwJ99m_jaV2zSMNwe3rz4GD0lO7tV-eI2nMTuYz-TWDwClXctB5e_0ryqIAFzfUMEdXMX6dvkt4fd4fsGYuTCpnrjX_P3uLVjQYmRbAQdD55jcKE3TYzch8Biko/s1600/alert-box-xss.gif" style="-webkit-box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; background-attachment: initial; background-clip: initial; background-image: initial; background-origin: initial; background-position: initial; background-repeat: initial; background-size: initial; border: 1px solid rgb(238, 238, 238); box-shadow: rgba(0, 0, 0, 0.0980392) 1px 1px 5px; box-sizing: border-box; max-width: 100%; padding: 5px; position: relative;" width="200" /></a></div>
<br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span class="Apple-style-span" style="background-color: white; color: #38761d; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 19px; font-weight: bold;">Types of XSS Based on persisting capability:</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Based one Persistence capability, we can categorize the XSS attack into two types namely Persistent and Non-Persistent.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"><span class="Apple-style-span" style="color: #38761d;">Persistent XSS:</span></b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">The Persistent or Stored XSS attack occurs when the malicious code submitted by attacker is saved by the server in the database, and then permanently it will be run in the normal page.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><i style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">For Example:   </i><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Many websites host a support forum where registered users can ask their doubts by posting message  , which are stored in the database.  Let us imagine , An attacker post a message containing malicious javascript code instead.  If the server fail to sanitize the input provided, it results in execution of injected script.  The code will be executed whenever a user try to read the post. If suppose the injected code is cookie stealing code, then it will steal cookie of users who read the post. Using the cookie, attacker can take control of </span><span class="IL_AD" id="IL_AD5" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">your account</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"><span class="Apple-style-span" style="color: #38761d;">Non-Persistent XSS:</span></b><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Non-Persistent XSS, also referred as Reflected XSS , is the most common type of XSS found now a days. In this type of attack, the injected code will be send to the server via HTTPrequest.  The server embedd the input with the html file and return </span><span class="IL_AD" id="IL_AD8" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">the file</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">(HTTPResponse) to browser.  When the browser executes the HTML file, it also execute the embedded script.  This kind of XSS vulnerability frequently occur in search fields.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><i style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Example:</i><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">Let us consider a project </span><span class="IL_AD" id="IL_AD4" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">hosting</span><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"> website.  To find our favorite project, we will just input the related-word in the search box .  When searching is finished, it will display a message like this "search results for yourword " .  If the server fail to sanitize the input properly, it will results in execution of injected script.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">In case of reflected XSS attacks, attacker will send the specially-crafted link to victims and trick them into click the link. When user click the link, the browser will send the injected code to server, the server reflects the attack back to the users' browser.  The browser then executes the code .</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">In addition to these types, there is also third  type of attack called DOM Based XSS attack, i will explain about this attack in later posts.</span><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><br style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;" /><b style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;"><span class="Apple-style-span" style="color: #990000;">What can an attacker do with this Vulnerability?</span></b><br />
<ul class="checklist" style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 1.4; margin: 0.5em 0px; padding: 0px 2.5em;">
<li style="margin: 0px 0px 0.25em; padding: 0px;">Stealing the Identity and Confidential Data(<span class="IL_AD" id="IL_AD3">credit</span> card details).</li>
<li style="margin: 0px 0px 0.25em; padding: 0px;">Bypassing restriction in websites.</li>
<li style="margin: 0px 0px 0.25em; padding: 0px;">Session Hijacking(Stealing session)</li>
<li style="margin: 0px 0px 0.25em; padding: 0px;">Malware Attack</li>
<li style="margin: 0px 0px 0.25em; padding: 0px;">Website Defacement</li>
<li style="margin: 0px 0px 0.25em; padding: 0px;">Denial of Service attacks(Dos)</li>
</ul>
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<b><span class="Apple-style-span" style="color: #38761d;"></span></b><br /><div style="margin: 0px;">
<b><span class="Apple-style-span" style="color: #38761d;"><i><b>Bypassing The XSS Filter Technique: XSS Tutorial Part 2(Coming Soon..!!)</b></i></span></b></div>
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<b><span class="Apple-style-span" style="color: #38761d;"><i><br /></i></span></b></div>
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<b><span class="Apple-style-span" style="color: #cc0000;">Disclaimer:</span></b></div>
<span style="background-color: white; color: #666666; font-family: 'Trebuchet MS', Trebuchet, Verdana, sans-serif; font-size: 15.8400001525879px; line-height: 20.5919990539551px;">This article is intended for educational purpose only.</span></div>
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What is XSS (Cross Site Scripting)

What is XSS? Cross Site Scripting also known as XSS , is one of the most common web appliction vulnerability that allows an attacker to...

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