Security Update 2005-005
If you're still running Panther (how gauche!), you'll want to run Software Update to grab Security Update 2005-005 for 10.3.9 Client and Server.
The Client update weighs in at 5.9MBs and "delivers a number of security enhancements and is recommended for all Macintosh users. This update includes the following components: Apache, AppKit, AppleScript, Bluetooth, Finder, Foundation, Help Viewer, lukemftpd, sudo, Terminal, VPN, and X11."
Get it now. . . . or update to Tiger now. Your call.