The System Only Wrapper (SOW) implementation in Mozilla Firefox before 20.0, Firefox ESR 17.x before 17.0.5, Thunderbird before 17.0.5, Thunderbird ESR 17.x before 17.0.5, and SeaMonkey before 2.17 does not prevent use of the cloneNode method for cloning a protected node, which allows remote attackers to bypass the Same Origin Policy or possibly execute arbitrary JavaScript code with chrome privileges via a crafted web site.