Yes, that is a scam and you should never respond. If you get a pop-up message asking to update Firefox or plugins or scanning for malware then such a message is likely a scam and you should NEVER respond to such an alert to avoid getting infected with malware. *only update Firefox via "Help -> About" or by downloading and installing Firefox from the Mozilla server and never via a pop-up or link on a web page. *plugins should only be updated via the plugin itself or by visiting the home page of the plugin. See also: *https://support.mozilla.org/en-US/kb/i-found-fake-firefox-update