Vulnerability Instance

shutdown reported a method of injecting running JavaScript code into
a page on another site using a modal alert to suspend an event handler
while a new page is being loaded. This vulnerability allows an attacker
to steal any confidential information the new page might contain,
including any passwords and cookies which might allow the attacker
to log on to that site as the victim.shutdown also reported a variant using the two-argument form of eval() that
did not require a modal dialog and would be much less obtrusive.
moz_bug_r_a4 reported two variants that bypassed our initial fixes,
one using "new Script()", the other extending the eval() attack using
window.__proto__Thunderbird shares the browser 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.