A few days ago Snow Leopard users found themselves unable to use any Java applications and games as Apple had blocked Java 6 from running on the operating system. It was because of vulnerabilities that were so problematic that the U.S. Department for Homeland Security actually released a statement advising computer users to disable the plugin.
Mountain Lion and Lion users had an update released to them last Friday that allowed them to start using Java somewhat safely again as Oracle was in charge of updates. For older versions of Java, Apple took over responsibility as Oracle wasn’t interested in maintaining legacy versions.
According to some analysis ~30% of Java users don’t bother to update the software leaving them open to massive security holes. This is such a problem given that Java is very widespread and with so many documented holes, along with a web plugin, it’s a hackers dream. A huge amount of people it will work on, and they don’t even have to be tricked into downloading a piece of software – they just have to click run on a Java pop-up. If you haven’t already, update your Java and consider about disabling it all together if you don’t make much use of it.