The JSSubScriptLoader in Mozilla Firefox 4.x through 6 and SeaMonkey before 2.4 does not properly handle XPCNativeWrappers during calls to the loadSubScript method in an add-on, which makes it easier for remote attackers to gain privileges via a crafted web site that leverages certain unwrapping behavior.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A14121
https://bugzilla.mozilla.org/show_bug.cgi?id=653926
http://www.mozilla.org/security/announce/2011/mfsa2011-43.html
http://www.mandriva.com/security/advisories?name=MDVSA-2011:141