CFNetwork in Apple iOS before 8.3 does not delete HTTP Strict Transport Security (HSTS) state information in response to a Safari history-clearing action, which allows attackers to obtain sensitive information by reading a history file.
https://support.apple.com/HT204661
http://www.securitytracker.com/id/1032050
http://www.securityfocus.com/bid/73978
http://lists.apple.com/archives/security-announce/2015/Apr/msg00002.html