Plugin Check service, which used to alert Firefox users about outdated plugins is no longer used by Mozilla to inform user about the plugin status, instead the company has relied on the add-ons blocklist they maintain on AMO for that.
Mozilla has now decided to remove all plugin check page links – which you generally see in Plugins section of Add-ons manager- from Firefox product and the browser vendor has also removed the support for the annoying outdated plugins prompt that displays on startup.
Firefox 50: Mozilla Plugin Check page links removed
” plugincheck is not an important part of our security strategy for Firefox any more, and is a continuing source of frustration for users when the blocklist doesn’t match plugincheck. We’re going to remove all plugincheck links from the product, and rely on the blocklist to inform users when their plugins are out of date.”
“This means that all future plugin blocks should be issued with an infoURL, or users will be directed to the AMO blocklist page, which is rarely useful.”
The target milestone for this change was set to Firefox 50, Yes! This will ride the trains.