Hi, yes it is a scam. Problem is it is in your computer or the site you visited and not Firefox problem though it maybe effecting Firefox. To fix this needs you to do so. Please use more than 1 scanner as each uses diff tech :

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Save your Report and google each before deleting anything as do not want to delete something you need, If need help :

• https://forums.malwarebytes.com/topic/9573-im-infected-what-do-i-do-now/

Post in only 1 forum, then wait.

Please let us know if this solved your issue or if need further assistance.

As a supplement to general cleaning tools:

(1) If you check your downloads history (Ctrl+j), do you see anything recent that could be related to unwanted software or an untrusted site?

(2) Please also check your extensions. You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions.

Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious or that you just do not remember installing or why? If in doubt, disable (or remove).

krackers said

I got a FFpopup saying to download/install ffinst25 but then FF said not to do it, now what? I clicked on download in the popup and then firefox said not to go to the web site. I am using windows 10 and firefox 59.0.2 Was it a scam? If so I hope Firefox will quickly fix it.

This did NOT come from the Firefox web browser or from Mozilla as it is a Fake site in the scammers attempt to trick less experienced users into infecting their Firefox install.

Firefox updates have always only been by way of download from mozilla.org like say www.mozilla.org/firefox/all/ or by internal software update in Firefox (with a .mar file) and never by some random download on some random weird name site.

This fake firefox update site has actually been recently discussed in https://malwaretips.com/blogs/remove-big-searches/

May of the blocked extensions listed on addons.mozilla.org/blocked with FF in name have been from these same disposable Fake "Firefox requires a manual update" sites.

Report the ffinst25.download site in https://www.mozilla.org/about/legal/fraud-report/ as it may help to get the site blocked or taken down.

i put into my computer: Malwarebytes, Avast Internet Security and Super Antispyware and ran all three. None indicated I have any problem(s). As best I can recall at the time I was on Time Magazine website and leaving for Slate when this popped up. Since this there has been no problems with the functioning of my computer. I guess not installing saved me bigger problems. I appreciate the detailed advice. Thank you very much.