Mozilla Firefox before 23.0, Firefox ESR 17.x before 17.0.8, Thunderbird before 17.0.8, Thunderbird ESR 17.x before 17.0.8, and SeaMonkey before 2.20 do not properly handle the interaction between FRAME elements and history, which allows remote attackers to conduct cross-site scripting (XSS) attacks via vectors involving spoofing a relative location in a previously visited document.