Mozilla Firefox before 17.0, Firefox ESR 10.x before 10.0.11, Thunderbird before 17.0, Thunderbird ESR 10.x before 10.0.11, and SeaMonkey before 2.14 implement cross-origin wrappers with a filtering behavior that does not properly restrict write actions, which allows remote attackers to conduct cross-site scripting (XSS) attacks via a crafted web site.