WebKit, as used in Apple Safari before 6.1.4 and 7.x before 7.0.4, does not properly interpret Unicode encoding, which allows remote attackers to spoof a postMessage origin, and bypass intended restrictions on sending a message to a connected frame or window, via crafted characters in a URL.
http://www.securityfocus.com/bid/67554
http://support.apple.com/kb/HT6254
http://archives.neohapsis.com/archives/bugtraq/2014-06/0174.html
http://archives.neohapsis.com/archives/bugtraq/2014-05/0128.html