Oracle has released an important update for the Java plugin, after a vulnerability was discovered in the Java Deploymente kit, a plugin that provides developers a simple method to distribute applications to end users. The plugin is installed by default with the Java Run-time Environment.
The vulnerability was disclosed on April 9, so Mozilla proceeded to block the plugin, and, most likely, it is already blocked and you are not affected by it.
To get the fix, visit java Web site and download Java 6 Update 20 (about 15MB), available for Windows, Linux and Solaris. Mac OS X users should use the Software Update feature to get it.