Integer overflow in the nsSVGFEMorphologyElement::Filter function in Mozilla Firefox before 15.0, Firefox ESR 10.x before 10.0.7, Thunderbird before 15.0, Thunderbird ESR 10.x before 10.0.7, and SeaMonkey before 2.12 allows remote attackers to execute arbitrary code via a crafted SVG filter that triggers an incorrect sum calculation, leading to a heap-based buffer overflow.