Incomplete blacklist vulnerability in CoreTypes in Apple Mac OS X before 10.6.3 makes it easier for user-assisted remote attackers to execute arbitrary JavaScript via a web page that offers a download with a Content-Type value that is not on the list of possibly unsafe content types for Safari, as demonstrated by the values for the (1) .ibplugin and (2) .url extensions.
http://support.apple.com/kb/HT4077
http://lists.apple.com/archives/security-announce/2010//Mar/msg00001.html