What is DOM-based XSS?

Question

DOM-based XSS is so poorly documented. I already know what reflected and stored XSS are.

Answer 1

Here are good resources for it:

• DOM Based XSS
• Testing for DOM-based Cross site scripting

DOM Based XSS (or as it is called in some texts, “type-0 XSS”) is an XSS attack wherein the attack payload is executed as a result of modifying the DOM “environment” in the victim’s browser used by the original client side script, so that the client side code runs in an “unexpected” manner. That is, the page itself (the HTTP response that is) does not change, but the client side code contained in the page executes differently due to the malicious modifications that have occurred in the DOM environment.

Answer 2

See http://www.owasp.org/index.php/DOM_Based_XSS

Basically, it's an attack aganist client-side scripts that fetch data from GET strings, the url, the fragment identifier or something like that and put it into the page without escaping it.