Yesterday, Apple released iCal 1.5.4, which is a security enhancement to help protect your computer when importing events with alarms that open files or applications. This is a 7.7MB download, and right now it is only available via the Mac OS X Software Update. From the Apple site:
What’s New in iCal 1.5.4
iCal 1.5.4 includes a new security improvement for imported events with alarms. iCal 1.5.2, the previous release, included enhancements in the Info Drawer, To Do alarms and notes, keyboard shortcuts, time zone support, publishing and subscribing behind firewalls, and other stability and performance improvements.
Synchronizing iCal 1.5.4
To synchronize your iCal information with mobile phones, PDAs, iPods or other Macs, iCal 1.5.4 requires iSync 1.2.1 or later. Equivalent versions of iCal and iSync are required in every Mac that is being synchronized. Install iCal before installing iSync.
Mac OS X v10.2.3 or later
Publishing calendars on the Internet requires a .Mac membership or a WebDAV server.