AppleKeyStore in Apple iOS before 8.3 does not properly restrict a certain passcode-confirmation interface, which makes it easier for attackers to verify correct passcode guesses via a crafted app.
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