Java for Mac OS X 10.6 has just been updated to Update 5, and a visit to Software Update will bring the latest and greatest version of Java to your Mac. If you're still using Leopard, Java for Mac OS X 10.5 is now at Update 10.
According to the release notes, "Java for Mac OS X 10.6 Update 5 delivers improved reliability, security, and compatibility for Java SE 6. Java for Mac OS X 10.6 Update 5 supersedes all previous versions of Java for Mac OS X 10.6." The Snow Leopard release is only for Mac OS X 10.6.6 and later. The Leopard updater is available for Mac OS X 10.5.8 and Mac OS X Server 10.5.8.
The security notes for the updates state that the new version fixes "multiple vulnerabilities in Java 1.6.0_24, the most serious of which may allow an untrusted Java applet to execute arbitrary code outside the Java sandbox." The updaters bump Java to version 1.6.0_26.
http://support.apple.com/kb/HT4593 has more details about the updates.
http://support.apple.com/kb/HT1222 will be the location for information about the security content of the updates, although that information had not yet been posted by Apple at the time this article was written.
You can check out all our software update posts on the right hand side of TUAW.com or on this page.