This is useful as a vector because it doesn't require a close angle bracket. This assumes there is any HTML tag below where you are injecting this cross site scripting vector. Using an open angle bracket at the end of the vector instead of a close angle bracket causes different behavior in Netscape Gecko rendering.
Without it, Firefox will work but Netscape won't:. The XSS locator uses this method. Fairly esoteric issue dealing with embedding images for bulleted lists. This will only work in the IE rendering engine because of the JavaScript directive. Not a particularly useful cross site scripting vector:. It can be used in similar XSS attacks to the one above this is the most comprehensive list on the net, at the time of this writing. Using something as simple as a remote style sheet you can include your XSS as the style parameter can be redefined using an embedded expression.
This only works in IE and Netscape 8. Notice that there is nothing on the page to show that there is included JavaScript. Note: With all of these remote style sheet examples they use the body tag, so it won't work unless there is some content on the page other than the vector itself, so you'll need to add a single letter to the page to make it work if it's an otherwise blank page:. A slight variation on this vector was used to hack Google Desktop.
This is useful if you cannot have either an equals sign or a slash in your cross site scripting attack, which has come up at least once in the real world:. This only works in Opera 8. This only works in Gecko rendering engines and works by binding an XUL file to the parent page. I think the irony here is that Netscape assumes that Gecko is safer and therefor is vulnerable to this for the vast majority of sites:.
This is a little different than the above two cross site scripting vectors because it uses an. The example file works by pulling in the JavaScript and running it as part of the style attribute:.
This is more useful against web application firewall cross site scripting evasion than it is server side filter evasion. The odd thing about meta refresh is that it doesn't send a referrer in the header - so it can be used for certain types of attacks where you need to get rid of referring URLs:. Directive URL scheme. This is nice because it also doesn't have anything visibly that has the word SCRIPT or the JavaScript directive in it, because it utilizes base64 encoding.
Please see RFC for more details or go here or here to encode your own. IFrames and most other elements can use event based mayhem like the following Submitted by: David Cross. This has been modified slightly to obfuscate the URL parameter. The original vulnerability was found by Renaud Lifchitz as a vulnerability in Hotmail:.
Rnaske built a quick XSS fuzzer to detect any erroneous characters that are allowed after the open parenthesis but before the JavaScript directive in IE and Netscape 8. These are in decimal but you can include hex and add padding of course.
Any of the following chars can be used: , 34, 39, , A variant of this was effective against a real world cross site scripting filter using a newline between the colon and "expression":.
Only works in IE5. Some websites consider anything inside a comment block to be safe and therefore does not need to be removed, which allows our Cross Site Scripting vector. Or the system could add comment tags around something to attempt to render it harmless. As we can see, that probably wouldn't do the job:. Works in IE and Netscape 8. If they allow objects, you can also inject virus payloads to infect the users, etc.
This example only works in Firefox, but it's better than the above vector in Firefox because it does not require the user to have Flash turned on or installed. Thanks to nEUrOO for this one. The XSS filter can make safe sites unsafe. I don't know enough about your site to judge if this may be a solution, but you can probably try. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. IE8 XSS filter: what does it really do? Ask Question. Asked 11 years, 10 months ago.
Active 10 years, 7 months ago. Viewed 46k times. Improve this question. Ned Batchelder Ned Batchelder k 69 69 gold badges silver badges bronze badges. Add a comment. Active Oldest Votes. What does it really do? It allows third parties to link to a messed-up version of your site.
So if you've got a clue about webapp authoring and you've been properly escaping output to HTML like a good boy, it's definitely a good idea to disable this unwanted, unworkable, wrong-headed intrusion by outputting the header: X-XSS-Protection: 0 in your HTTP responses.
Improve this answer. You are right, hp. I had assumed that it needed to come from AOL. But this is a way for hp. Well, it might also be vulnerable, but that's another issue ;- — bobince. If yes— proceed to next check If no — bypass XSS Filter and continue loading Is a "document" load like a frame, not a subdownload?
Referrer header: Does the final post-redirect fully-qualified domain name in the HTTP request referrer header match the fully-qualified domain name of the URL being retrieved? If yes — modify the response. EricLaw EricLaw 55k 7 7 gold badges silver badges bronze badges.
XSS filtering by the browser can only be effective against reflected XSS attacks, where the malicious code injected by the attacker is directly reflected in the client browser. Server-side filters, in turn, can help against reflected and stored XSS but are helpless against DOM-based attacks, as the exploit code never arrives at the server.
And while input filtering by the web application itself can theoretically detect all types of XSS attacks, it comes with its own serious limitations — it can interfere with automated filters and requires frequent updates to keep up with new exploits. XSS filtering adds an extra level of difficulty to the work of attackers crafting XSS attacks, as any successfully injected script code also has to get past the filters.
While XSS attacks generally target application vulnerabilities and misconfigurations, evasion techniques exploit weaknesses in the browser or server-side filters, down to specific products and versions. As shown below, countless evasion approaches exist, but the common denominator is that they all abuse product-specific implementations of web technology specifications.
XSS filter evasion techniques take advantage of this complex tangle of languages, specifications, exceptions, and browser-specific quirks to slip malicious code past the filters. Filter evasion techniques can attempt to exploit any aspect of web code parsing and processing, so there are no rigid categories here.
The most obvious attempts to inject script tags will generally be rejected, but other HTML tags can also provide injection vectors. Event handlers are often used to trigger script loading, as they can be tied into legitimate user actions. Commonly exploited handlers include onerror , onclick , and onfocus , but the majority of supported event handlers can be used as XSS vectors.
To bypass filters that rely on scanning text for specific suspicious strings, attackers can encode any number of characters in a variety of ways:. Browsers are very lenient when it comes to whitespace in HTML and JavaScript code, so embedded non-printing characters can be used for bypassing filters:. Because of its many non-standard implementations and quirks related to integration with other Microsoft technologies, Internet Explorer provides some unique filter evasion vectors.
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