Incomplete blacklist vulnerability in CoreTypes in Apple Mac OS X before 10.5.4 allows user-assisted remote attackers to execute arbitrary code via a (1) .xht or (2) .xhtm file, which does not trigger a "potentially unsafe" warning message in (a) the Download Validation feature in Mac OS X 10.4 or (b) the Quarantine feature in Mac OS X 10.5.
https://exchange.xforce.ibmcloud.com/vulnerabilities/43493
http://www.vupen.com/english/advisories/2008/1981/references
http://www.securityfocus.com/bid/30018
http://support.apple.com/kb/HT2163
http://securitytracker.com/id?1020391
http://secunia.com/advisories/30802
http://lists.apple.com/archives/security-announce/2008//Jun/msg00002.html