There is a massive security threat affecting numerous websites wordwide and the only way to be safe is to disable Java or remove Java from your system. Apple has blacklisted Java in more recent versions of the OS.
The Ars Technica site has links on how to disable or remove Java.
I think Firefox has already done this? It is already disabled on my system - I think!
Java Plugin 7 update 10 and lower (click-to-play), Windows has been blocked for your protection.
Why was it blocked?
The Java plugin is causing significant security problems. All users are strongly recommended to keep the plugin disabled unless necessary.
Who is affected?
All users who have these versions of the plugin installed in Firefox 17 and above.
What does this mean?
The problematic add-on or plugin will be automatically disabled and no longer usable.
When Mozilla becomes aware of add-ons, plugins, or other third-party software that seriously compromises Firefox security, stability, or performance and meets certain criteria, the software may be blocked from general use. For more information, please read this support article.
Blocked on October 30, 2012. View block request.