Mozilla Firefox 3.6.x before 3.6.7 and Thunderbird 3.1.x before 3.1.1 do not properly implement access to a content object through a SafeJSObjectWrapper (aka SJOW) wrapper, which allows remote attackers to execute arbitrary JavaScript code with chrome privileges by leveraging "access to an object from the chrome scope."
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.