Launchpad.net

CVE 2012-1956

Mozilla Firefox before 15.0, Thunderbird before 15.0, and SeaMonkey before 2.12 do not prevent use of the Object.defineProperty method to shadow the location object (aka window.location), which makes it easier for remote attackers to conduct cross-site scripting (XSS) attacks via vectors involving a plugin.

See the CVE page on Mitre.org for more details.