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 do not ensure the correctness of the address bar during history navigation, which allows remote attackers to conduct cross-site scripting (XSS) attacks or phishing attacks by leveraging control over navigation timing.