Apple released Security Update 2007-005 on Thursday. It is available via the Software Update in System Preferences of Mac OS X.
The PowerPC version is 16.7 MB while the Intel version is 30.2 MB.
This update is recommended for all users and improves security in these components: bind, CarbonCore, CoreGraphics, crontabs, fetchmail, file, iChat, mDNSResponder, PPP, ruby, screen, texinfo and VPN.
Additional details about each component patched are available at Apple.
After installation, there will be a double-boot sequence on both PPC and Intel.