Currently Firefox has no built-in mechanism for updating plug-ins (in the future Firefox will update plug-ins for you). So they have started an online service for that.
Now the plug-in check page is live and you can check the status of more than 15 popular plugins now and more will be added soon.
Visitors to the page can see which plugins they have installed on their browser and, for any that are outdated; follow an easy link to the update site. [via]