This indicates a possible exploit of a denial of service vulnerability in Mozilla Firefox and Thunderbird.
This vulnerability is triggered by document structure changes during a DOMNodeRemoved event.
Firefox versions prior to 220.127.116.11
Thunderbird versions prior to 18.104.22.168
SeaMonkey versions prior to 1.0.2
Denial of service.
Upgrade to Firefox 22.214.171.124, Thunderbird 126.96.36.199, and SeaMonkey 1.0.2 :