The Download Validation in Mail in Mac OS X 10.4 does not properly recognize attachment file types to warn a user of an unsafe type, which allows user-assisted remote attackers to execute arbitrary code via crafted file types.
https://exchange.xforce.ibmcloud.com/vulnerabilities/25027
http://www.vupen.com/english/advisories/2006/0791
http://www.us-cert.gov/cas/techalerts/TA06-062A.html
http://www.securityfocus.com/bid/16907
http://secunia.com/advisories/19064
http://lists.apple.com/archives/client-management/2006/Mar/msg00030.html