Apple has released a security update for OS X 10.3 users. The update fixes a flaw in QuickTime Java that could allow unauthorized access. From Apple:
Security Update 2003-10-28 addresses a potential vulnerability in the implementation of QuickTime Java in Mac OS X v10.3 and Mac OS X Server v10.3 that could allow unauthorized access to a system.
The update, available from Software Update for users of both the Client and Server versions of OS X 10.3, weighs in at 592KB, and requires a reboot.