The Apple ID OD plug-in in Apple OS X before 10.10.5 allows attackers to change arbitrary user passwords via a crafted app.
https://support.apple.com/kb/HT205031
http://www.zerodayinitiative.com/advisories/ZDI-15-390
http://www.securitytracker.com/id/1033276
http://www.securityfocus.com/bid/76340
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html