A potentially exploitable flaw was found in the way mozilla handled "loadSubScript". Reference: https://bugzilla.mozilla.org/show_bug.cgi?id=653926
David Rees reported that the JSSubScriptLoader (a feature used by some add-ons) was "unwrapping" XPCNativeWrappers when they were used as the scope parameter to loadSubScript(). Without the protection of the wrappers the add-on could be vulnerable to privilege escalation attacks from malicious web content. Whether any given add-on were vulnerable would depend on how the add-on used the feature and whether it interacted directly with web content, but we did find at least one vulnerable add-on and presume there are more. The unwrapping behavior was a change introduced during Firefox 4 development. Firefox 3.6 and earlier versions are not affected. Statement: Not vulnerable. This issue did not affect the versions of firefox as shipped with Red Hat Enterprise Linux 5 or 6.
External Reference: http://www.mozilla.org/security/announce/2011/mfsa2011-43.html