The XPCSafeJSObjectWrapper class in the SafeJSObjectWrapper (aka SJOW) implementation in Mozilla Firefox 3.6.x before 3.6.9 and Thunderbird 3.1.x before 3.1.3 does not properly restrict objects at the end of scope chains, which allows remote attackers to execute arbitrary JavaScript code with chrome privileges via vectors related to a chrome privileged object and a chain ending in an outer object.