this is the screenshot of the webpage

Hi, if you run into something like that again you can go to the 3 Bar Menu --> Help --> Report Deceptive Site.

Or : https://www.mozilla.org/en-US/about/legal/fraud-report/ and : https://safebrowsing.google.com/safebrowsing/report_phish/?hl=en

It is always good to give your self a scan after something like that : https://www.malwarebytes.com/

When you get a scam page that shows that two-line "Authentication Required" dialog, and you cancel it, usually the page will reload and show it again. To break the cycle, tap the Esc key several times in a row quickly. That should cancel the dialog as well as the reload. Then you can easily close the tab.

lalitkumar123 said

Recently while downloading some stuff from web, a pop up windows came which looks like mozilla but web address is different. i wanted to send it to mozilla people but i could not find any email address. Anyway, that pop up ask for a username and password and says that important components of your browser need to be updated. Also it is impossible to close it. Only way i could find is to kill firefox from task manager which eventually kills every tab i am working on.

Oh Mozilla knows about these type of fake update pages as there is even a article about them https://support.mozilla.org/en-US/kb/i-found-fake-firefox-update

Just report the url at https://www.mozilla.org/en-US/about/legal/fraud-report/ and https://safebrowsing.google.com/safebrowsing/report_phish/?tpl=mozilla&hl=en

The ESC key can help in closing the tab.

Also do not click on the green button and allow extension install as they hijack search engine and keep you from opening your Addons manager. Many of these fake extensions have been added to blockist at addons.mozilla.org/blocked/