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.
https://exchange.xforce.ibmcloud.com/vulnerabilities/50487
http://www.us-cert.gov/cas/techalerts/TA09-133A.html
http://support.apple.com/kb/HT3549
http://lists.apple.com/archives/security-announce/2009/May/msg00002.html