Launchpad.net

CVE 2011-2986

Mozilla Firefox 4.x through 5, Thunderbird before 6, SeaMonkey 2.x before 2.3, and possibly other products, when the Direct2D (aka D2D) API is used on Windows, allows remote attackers to bypass the Same Origin Policy, and obtain sensitive image data from a different domain, by inserting this data into a canvas.

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