The startDocumentLoad function in browser/base/content/browser.js in Mozilla Firefox 3.5.x before 3.5.11 and 3.6.x before 3.6.7, and SeaMonkey before 2.0.6, does not properly implement the Same Origin Policy in certain circumstances related to the about:blank document and a document that is currently loading, which allows (1) remote web servers to conduct spoofing attacks via vectors involving a 204 (aka No Content) status code, and allows (2) remote attackers to conduct spoofing attacks via vectors involving a window.stop call.
hg.mozilla.org/mozilla-central/rev/cadddabb1178
lcamtuf.blogspot.com/2010/06/yeah-about-that-address-bar-thing.html
secunia.com/advisories/40283
www.mozilla.org/security/announce/2010/mfsa2010-45.html
bugzilla.mozilla.org/show_bug.cgi?id=556957
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A8248