On the heels of the Mac OS X 10.3.9 comes a Security Update (2005-004) - in your Software Update:
Security Update 2005-004 delivers a number of security enhancements and is recommended for all Macintosh users. This update includes the following components:
iSync
For detailed information on this Update, please visit this website: http://www.info.apple.com/kbnum/n61798/
It addresses a potential buffer overflow issue in a iSync related application.