CVE 2009-1838
The garbage-collection implementation in Mozilla Firefox before 3.0.11, Thunderbird before 2.0.0.22, and SeaMonkey before 1.1.17 sets an element's owner document to null in unspecified circumstances, which allows remote attackers to execute arbitrary JavaScript with chrome privileges via a crafted event handler, related to an incorrect context for this event handler.
See the 
CVE page on Mitre.org
for more details.
