Integer overflow in the nsGenericDOMDataNode::SetTextInternal function in Mozilla Firefox 3.5.x before 3.5.10 and 3.6.x before 3.6.4, Thunderbird before 3.0.5, and SeaMonkey before 2.0.5 allows remote attackers to execute arbitrary code via a DOM node with a long text value that triggers a heap-based buffer overflow.