Cross-site scripting (XSS) vulnerability in Mozilla Firefox before 2.0.0.13, Thunderbird before 2.0.0.13, and SeaMonkey before 1.1.9 allows remote attackers to inject arbitrary web script or HTML via event handlers, aka "Universal XSS using event handlers."
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.