Use-after-free vulnerability in the nsTreeSelection 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 might allow remote attackers to execute arbitrary code via vectors involving a XUL tree selection, related to a "dangling pointer vulnerability." NOTE: this issue exists because of an incomplete fix for CVE-2010-2753.