The NS_SecurityCompareURIs function in netwerk/base/public/nsNetUtil.h in Mozilla Firefox before 3.5.16 and 3.6.x before 3.6.13, and SeaMonkey before 2.0.11, does not properly handle (1) about:neterror and (2) about:certerror pages, which allows remote attackers to spoof the location bar via a crafted web site.
lists.fedoraproject.org/pipermail/package-announce/2010-December/052022.html
lists.fedoraproject.org/pipermail/package-announce/2010-December/052032.html
lists.fedoraproject.org/pipermail/package-announce/2010-December/052502.html
lists.fedoraproject.org/pipermail/package-announce/2010-December/052504.html
lists.opensuse.org/opensuse-security-announce/2011-01/msg00002.html
secunia.com/advisories/42716
secunia.com/advisories/42818
support.avaya.com/css/P8/documents/100124650
www.mandriva.com/security/advisories?name=MDVSA-2010:251
www.mozilla.org/security/announce/2010/mfsa2010-83.html
www.redhat.com/support/errata/RHSA-2010-0966.html
www.securitytracker.com/id?1024850
www.ubuntu.com/usn/USN-1019-1
www.vupen.com/english/advisories/2011/0030
bugzilla.mozilla.org/show_bug.cgi?id=602780
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12512