CFNetwork HTTPProtocol in Apple iOS before 9.2 and OS X before 10.11.2 allows man-in-the-middle attackers to bypass the HSTS protection mechanism via a crafted URL.
http://lists.apple.com/archives/security-announce/2015/Dec/msg00000.html
http://lists.apple.com/archives/security-announce/2015/Dec/msg00005.html
http://www.securitytracker.com/id/1034344