The URL parsing implementation in Mozilla Firefox before 42.0 improperly recognizes escaped characters in hostnames within Location headers, which allows remote attackers to obtain sensitive information via vectors involving a redirect.
http://lists.opensuse.org/opensuse-security-announce/2015-11/msg00015.html
http://www.mozilla.org/security/announce/2015/mfsa2015-129.html
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
http://www.securitytracker.com/id/1034069
http://www.ubuntu.com/usn/USN-2785-1