The Time Machine server in Server App in Apple OS X Server before 5.1 does not notify the user about ignored permissions during a backup, which makes it easier for remote attackers to obtain sensitive information in opportunistic circumstances by reading backup data that lacks intended restrictions.
https://support.apple.com/HT206173
http://www.securitytracker.com/id/1035342
http://www.securityfocus.com/bid/85054
http://lists.apple.com/archives/security-announce/2016/Mar/msg00006.html