ImageIO in Apple iOS before 8.4.1 and OS X before 10.10.5 does not properly initialize an unspecified data structure, which allows remote attackers to obtain sensitive information from process memory via a crafted PNG image.
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html
http://lists.apple.com/archives/security-announce/2015/Aug/msg00002.html
https://support.apple.com/kb/HT205030