CVE 2006-0294
Mozilla Firefox before 1.5.0.1, Thunderbird 1.5 if running Javascript in mail, and SeaMonkey before 1.0 allow remote attackers to execute arbitrary code by changing an element's style from position:relative to position:static, which causes Gecko to operate on freed memory.
See the 
CVE page on Mitre.org
for more details.
