Accessing XBL compilation scope via valueOf.call()


moz_bug_r_a4 discovered that the compilation scope of privileged built-in
XBL bindings was not fully protected from web content and could be accessed
by calling valueOf.call() and valueOf.apply() on a method of that binding.
This could then be used to compile and run attacker-supplied JavaScript,
giving it the privileges of the binding which would allow an attacker to
install malware such as viruses and password sniffers.

shutdown  reported an alternate way to get to XBL compilation scope by
inserting an XBL method into the DOM's document.body prototype chain.

Note: Thunderbird shares the JavaScript engine with Firefox and could be
vulnerable if JavaScript were to be enabled in mail. This is not the default
setting and we strongly discourage users from running JavaScript in mail.

Workaround

Disable JavaScript until you can upgrade to a fixed version.

References

[1]https://bugzilla.mozilla.org/show_bug.cgi?id=312871
[2]https://bugzilla.mozilla.org/show_bug.cgi?id=313236
[3]https://bugzilla.mozilla.org/show_bug.cgi?id=313375


This issue also affects FC4