Mozilla Firefox before 2.0.0.15 and SeaMonkey before 1.1.10 allow remote attackers to bypass the Same Origin Policy and conduct cross-site scripting (XSS) attacks via vectors involving (1) an event handler attached to an outer window, (2) a SCRIPT element in an unloaded document, or (3) the onreadystatechange handler in conjunction with an XMLHttpRequest.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.