14 DAY TRIAL // Mozilla has provided an update on the Java blocklist that rolled out a couple of days ago. Mozilla wanted to softblock in Firefox older Java versions that were vulnerable to an attack.
This meant that the plugin would be disabled by default, but users had the option to keep it enabled if they wanted.
Instead, Mozilla issued a hardblock, which meant users were unable to run the older Java versions even if they were aware of the risks and wanted to anyway. For those that needed Java to work, this has been a problem.
Mozilla has fixed the issue, i.e. it issued a softblock, but it will take a while before the new blocklist gets to all Firefox users. Fortunately for affected users, there is a workaround which will enable them to run the older Java versions.
Note that the simplest way of fixing the problem is just to get the latest Java plugin, which has been patched for the vulnerability. Apple issued an updated version yesterday so now, even Mac OS X users can run a safe version. Mozilla still isn't issuing a block for Mac OS X though.
However, if updating to the latest Java is not an option, but you still want to run Java, roll up your sleeves and get ready for a bit of work.
Basically, what you need to do is delete the blocklist file from your computer and possibly one related to plugins as well. You need to find your Firefox Profile Directory, if you don't know where to look for it, simply type about:support in the address bar and then look for "Profile Directory" and click on the button next to it.
Once you've navigated to the profile folder, find blocklist.xml and delete it. Make sure Firefox is not running before you do this. You may also have to delete plguinreg.dat. Then go back to Firefox, go to about:addons and enable the Java plugin.