Mozilla Firefox before 16.0.1, Firefox ESR 10.x before 10.0.9, Thunderbird before 16.0.1, Thunderbird ESR 10.x before 10.0.9, and SeaMonkey before 2.13.1 omit a security check in the defaultValue function during the unwrapping of security wrappers, which allows remote attackers to bypass the Same Origin Policy and read the properties of a Location object, or execute arbitrary JavaScript code, via a crafted web site.