CVE 2011-2988
Buffer overflow in an unspecified string class in the WebGL shader implementation in Mozilla Firefox 4.x through 5, Thunderbird before 6, SeaMonkey 2.x before 2.3, and possibly other products allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a long source-code block for a shader.
See the 
CVE page on Mitre.org
for more details.
