No. Any popups that tell you your computer is infected, it's more than likely a scam or a trick to get you to install malware.

Get a good adblock like uBlock Origin and you'll never see these again. To get even more strict, use Popup Blocker (strict)

Also, Mozilla does not provide e-mail, telephone, or live chat support so there would be no reason to push a pop-up to you. Even if there WAS a reason for them to do so, they would choose a better format to do so.

I don't get the pop-up because they are blocked, but I do get the audio warning. It happens a couple of times a week and it may be connected to Outlook. Why hasn't Firefox done something about this? I reinstalled to see if that helped but no. So now it's off my computer and I'm using Safari. Do you think Firefox will fix this before I decide just to stick with Safari ???

Also see: https://support.mozilla.org/en-US/questions/1170371 for a similar fake.