Cerulean Studios Trillian 3.0 allows remote attackers to cause a denial of service (crash) via a reverse direct connection from a different client, as demonstrated using LICQ.
http://sourceforge.net/mailarchive/forum.php?thread_id=8315933&forum_id=5420
http://securityreason.com/securityalert/43
http://marc.info/?l=bugtraq&m=112837909626441&w=2
http://ceruleanstudios.com/forums/showthread.php?s=84987af3601384b1dc7ea1f36b237c9c&threadid=64889