Which Firefox add-on checks if the latest plugins are installed?
Is there a Firefox add-on that checks if I have the latest version of Adobe Flash, Sun Java, etc installed?
Although I did not find a plugin, Firefox has its own website to check this for you, known as "Plugin Check and Updates"
Actually, Firefox itself can check if there are updates for the installed add-ons. This can be activated/deactivated in the sttings -> updates or in the add-ons-tab (hidden behind the "gear" icon).