Apple released Security Update 2004-004 today, which includes a host of fixes for Mac OS X. A total of 25 updates have been posted, some of which fix flaws dangerous enough to cause arbitrary code execution. If you're using OS X, odds are you're already retrieving the updates, but if not you can always download
the 16MB blob of patches from Apple's site. You can read about the specific updates in the advisory
for the patch.