Directory traversal vulnerability in Mozilla Firefox before 2.0.0.4 on Windows allows remote attackers to read arbitrary files via ..%5C (dot dot encoded backslash) sequences in a resource:// URI.
https://bugzilla.mozilla.org/show_bug.cgi?id=367428
http://www.securityfocus.com/archive/1/470500/100/0/threaded
http://secunia.com/advisories/25481
http://larholm.com/2007/06/04/unpatched-input-validation-flaw-in-firefox-2004/
http://ha.ckers.org/blog/20070516/read-firefox-settings-poc/#comment-35888