Oracle has been forced to release another update to the Java plug-in due to critical security flaws present in the previous release. Java SE 7 update 15 was released yesterday, February 19, and contains patches that plug security holes that allowed Facebook and Apple to hacked. The update also features improvements in performance and stability.
The update will force users of Java SE 6 to upgrade to the latest version as long as their system can run Java SE 7. Version 6 of Java has been officially "retired" by the company and should not be used due to security risks that are present. If you still have Java installed on your system, you should update to the latest version without delay.