Apple released a Security Update for Mac OS X today:
Security Update 2004-01-26 delivers a number of security enhancements and is recommended for all Macintosh users. This update includes the following components: Apache 1.3, Classic, Mail, Safari, Windows File Sharing
Additionally, Security Update 2003-12-19 has been incorporated into this security update. Those components are: AFP Server, ASN.1 Decoding for PKI, cd9660.util, Directory Services, fetchmail, fs_usage, rsync, System Initialization