At the same time that Apple released an update to Leopard (10.5), the company also fixed a number of security issues for users running Tiger (10.4).
Security Update 2009-02 updates several areas of Tiger, including Apache, CoreGraphics, CUPS, Disk images, Flash Player plug-in, Help Viewer, Spotlight, X11, and more. It fixes problems ranging from keeping PDFs opened in CoreGraphics from executing malicious code to preventing maliciously crafted Mach-O executables from causing the Finder to repeatedly terminate and relaunch.
There are four version of the update, one each for Tiger client PowerPC and Intel, as well as Tiger Server PowerPC and Universal. All require you to be running 10.4.11, and the proper update should show up using Tiger’s Software Update mechanism.