Apart from including general OS improvements that enhance stability, compatibility, and security for a Mac, Apple has included 13 specific security updates.
Apple has announced its fourth update for its operating system (OS) Leopard -- Mac OS X 10.5.4. This update is recommended for Mac OS X 10.5, 10.5.1, 10.5.2, and 10.5.3 Leopard.
Apart from including general OS improvements that enhance stability, compatibility, and security for a Mac, Apple has included 13 specific security updates: Alias Manager, CoreTypes, c++filt, Dock, Launch Services, Net-SNMP, Ruby, SMB File Server, System Configuration, Tomcat, VPN, and WebKit.
The security update APPLE-SA-2008-004 for Mac OS X 10.5.4 can be downloaded and installed here.
This update is nothing like the 10.5.3 update, which brought extra dock greatness, etc. There are some performance issues and minor bugs that got fixed, but nothing that us users will notice much.