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.
Vulmon