hello, i think the plugin isn't active since firefox has blocklisted older versions of the java plugin - it contains various security vulnerabilites which are commonly exploited out there on the web & used for "drive-by-infections" (it's enough to just visit a malicious page, no further interaction is needed).

do you have the possibility to update to the current version of java on this computer?

https://addons.mozilla.org/firefox/blocked/p80

It's not that plugin isn't active. Plugin doesn't even show on about:plugins as inactive. And I do not see that error you've posted. I think FF isn't aware that there is Java installed nor it's version.

And sadly updating/reinstalling Java or Firefox is not an option for me.

ok, i read about this problem on the mozillazine kb now...

could you try the following: go to start run & open %appdata%\Mozilla\, in there create a folder named plugins (in case it doesn't exist yet). then you'd have to go into the java program directory and the bin subfolder (probably C:\Program Files\Java\j2re<version>\bin\) & copy all .dll-files that start with np*.dll and paste them into the plugins folder, that you have created before. this has to be repeated for every user on the machine.

in case firefox is detecting the plugin afterwards, i would recommend you keep the plugin disabled and only enable it on demand (or use an extension like noscript to create a whitelist for trusted sites that can use the plugin). i've seen many infections myself that exploited the vulnerabilities in old java versions, also on accounts with limited user rights...

It worked. However now FF blocked this like you said it would. I disabled extensions.blocklist.enabled just to test if it works. Then plugin shows as enabled but it's still not working. No idea why.

what result do you get when you visit this java test site? http://www.java.com/en/download/testjava.jsp

See the screen.

well this actually looks good since it is stating "old versions of java has been detected on your system" - when i view the page with java disabled only the bottom part is showing up. obviously oracle will warn you too that the plugin is outdated & is trying to get you updating...

It would solve all the problems but I can't do it. And admin isn't too keen on updating Java on single machine. This looks like a dead end.

does this site work? http://www.cis.upenn.edu/~matuszek/Ge.../JavaTests.html

i understand that the admin won't like changing the configuration on a single machine, but please urge him to upgrade the whole environment. here is oracles own advisory: http://www.oracle.com/technetwork/topics/security/javacpufeb2012-366318.html

All tests failed. Adding screens.

I know benefit of the update however this is not that easy.

the mozillazine kb has a section named "Missing plugin alert even though Java is installed" and it also refers to the registry entry that you already hat suspected in your question... unfortunately it seems that it is not possible to work around the issue without admin rights.

I guess so. Anyways, thank you for the help!