Mozilla Firefox 4.x through 6, Thunderbird before 7.0, and SeaMonkey before 2.4 do not prevent manual add-on installation in response to the holding of the Enter key, which allows user-assisted remote attackers to bypass intended access restrictions via a crafted web site that triggers an unspecified internal error.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A14442
https://bugzilla.mozilla.org/show_bug.cgi?id=672485
http://www.mozilla.org/security/announce/2011/mfsa2011-40.html
http://www.mandriva.com/security/advisories?name=MDVSA-2011:142
http://www.mandriva.com/security/advisories?name=MDVSA-2011:141
http://www.mandriva.com/security/advisories?name=MDVSA-2011:140
http://www.mandriva.com/security/advisories?name=MDVSA-2011:139
http://secunia.com/advisories/46315
http://lists.opensuse.org/opensuse-updates/2011-10/msg00002.html
http://lists.opensuse.org/opensuse-security-announce/2011-11/msg00020.html