The nsTreeContentView function in Mozilla Firefox before 3.5.12 and 3.6.x before 3.6.9, Thunderbird before 3.0.7 and 3.1.x before 3.1.3, and SeaMonkey before 2.0.7 does not properly handle node removal in XUL trees, which allows remote attackers to execute arbitrary code via vectors involving access to deleted memory, related to a "dangling pointer vulnerability."