iChat in Apple Mac OS X 10.5 before 10.5.7 disables SSL for AOL Instant Messenger (AIM) communication in certain circumstances that are inconsistent with the Require SSL setting, which allows remote attackers to obtain sensitive information by sniffing the network.
http://lists.apple.com/archives/security-announce/2009/May/msg00002.html
http://secunia.com/advisories/35074
http://support.apple.com/kb/HT3549
http://www.securityfocus.com/bid/34926
http://www.securitytracker.com/id?1022212
http://www.us-cert.gov/cas/techalerts/TA09-133A.html