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 restrict local-filesystem access by Java applets, which allows user-assisted remote attackers to read arbitrary files by leveraging a download to a fixed pathname or other predictable pathname.