The Podcasts component in Apple iOS before 8.3 and Apple TV before 7.2 allows remote attackers to discover unique identifiers by reading asset-download request data.
https://support.apple.com/HT204662
https://support.apple.com/HT204661
http://www.securitytracker.com/id/1032050
http://www.securityfocus.com/bid/73983
http://lists.apple.com/archives/security-announce/2015/Apr/msg00003.html
http://lists.apple.com/archives/security-announce/2015/Apr/msg00002.html