Apple has posted a security update for iSync to address an issue with a component of the synchronization software called mRouter. The buffer overflow vulnerability the security update corrects could allow an intruder to gain root access to your Mac.
Security Update 2005-004 is for iSync 1.5 in Mac OS X v10.2.8 and Mac OS X v10.3.x. The download weighs in at 1.1 megabytes, and can be downloaded through Software Update in Mac OS X.
TMO recommends the update for all users.
You can read more about the update at Appleis support Web site. The company credited Braden Thomas for reporting the issue.