Oracle has released its quarterly security fixes for Java. The new Version 6 Update 31, addresses 14 identified security vulnerabilities; at least one of these is extremely serious, because it can be exploited remotely without a login. (There is also a Version 7 Update 3 available for developers, with the same fixes.) Further information is available in the Critical Patch Update Advisory.
The new version is available for almost all platforms: Linux, Windows, and Solaris. Apple supplies its own versions of Java for Mac OS X; there is usually a time lag of at least a few days after Oracle releases a new version before an updated Mac version is available
Because of the security content of this release, if you have Java installed ono your system, I recommend that you install this update as soon as you conveniently can. You can obtain the new version, including the browser plug-in, from the Java download page. Windows users can also use automatic updates to get the new release.

[...] These versions correspond to Java Version 6 Update 31, released for other platforms by Oracle in February. (As Mac users probably know, Apple packages and releases its own Java [...]