The Swift implementation in Apple Xcode before 7.1 mishandles type conversion, which has unspecified impact and attack vectors.
https://support.apple.com/HT205379
https://euvd.enisa.europa.eu/vulnerability/EUVD-2015-6962
http://www.securitytracker.com/id/1033930
http://lists.apple.com/archives/security-announce/2015/Oct/msg00008.html