hello mike, yes this is a scam tactic that is trying to trick you into installing malware, so don't download or execute this kind of stuff! updates are handled automatically by firefox so you don't have to download anything (you can initiate a check for updates in firefox > help > about firefox).

you might also want to run a full scan of your system with the security software already in place and different tools like the free version of malwarebytes, adwcleaner & kaspersky security scan in order to make sure that there isn't already some sort of malware active on your system that triggers these false alerts.

Troubleshoot Firefox issues caused by malware

Thanks <philipp> I got the same thing, while doing multiple searches on eBay-UK; and immediately thought it suspicious too. But how many FireFox users, duped by this scamming fissure, will load god-knows-what malware? I can't be absolutely sure if there's any connection with any eBay listing(s): two trojans or pups may have arrived earlier, from elsewhere; then hijacked my firefox tab later. I have now found and deleted them both with Malwarebytes-free; which I only use irregularly as a second-line antimalware program. Like most days, I did also run Iobit.com's similarly free and effective MalwareFighter at the end of my session only yesterday; so I'm confident the pups arrived today.

Please restart FF with all addons disabled. Its from one of the addons.

Check their options and disable marketing from their options. One such addon is flv movies downloader