The private-browsing implementation in WebKit in Apple Safari before 6.2.8, 7.x before 7.1.8, and 8.x before 8.0.8 does not prevent caching of HTTP authentication credentials, which makes it easier for remote attackers to track users via a crafted web site.
https://support.apple.com/kb/HT205033
http://www.securitytracker.com/id/1033274
http://www.securityfocus.com/bid/76339
http://lists.opensuse.org/opensuse-updates/2016-03/msg00054.html
http://lists.apple.com/archives/security-announce/2015/Aug/msg00000.html