Office Viewer in Apple iOS before 8.4.1 and OS X before 10.10.5 allows remote attackers to read arbitrary files via an XML document containing an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue.
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html
http://lists.apple.com/archives/security-announce/2015/Aug/msg00002.html
http://lists.apple.com/archives/security-announce/2015/Oct/msg00000.html
https://support.apple.com/HT205373
https://support.apple.com/kb/HT205030