CVE 2013-1674
Use-after-free vulnerability in Mozilla Firefox before 21.0, Firefox ESR 17.x before 17.0.6, Thunderbird before 17.0.6, and Thunderbird ESR 17.x before 17.0.6 allows remote attackers to execute arbitrary code via vectors involving an onresize event during the playing of a video.
See the 
CVE page on Mitre.org
for more details.
