Spontaneous phishing site in Firefox

This malicious website appears spontaneously in Firefox, replacing the site I was viewing in the same tab.

http://159.89.80.249/asr4/?a=10012592&campid=46#

What is failing to stop a non-selected website from appearing in a browser window?
If I copy the url of this website and open in a new tab I get the Firefox warning screen:"Deceptive Site Ahead." This screen does not appear when the non-selected website opens spontaneously, so it is harder to determine if I'm being phished.

(Recent Dell PC, Windows 10 home deluxe, latest Firefox, etc.)

Hi Fred,

Without me being able to see what is happening it is hard to estimate what the situation is.

This might be happening because of any Browser Add-Ons or any recently installed Application. I request you Reset your Browsers and check if that resolves the issue. Also, please check for any unknown applications that have been installed recently and uninstall them.

Hi Fred,

Without me being able to see what is happening it is hard to estimate what the situation is.

This might be happening because of any Browser Add-Ons or any recently installed Application. I request you Reset your Browsers and check if that resolves the issue. Also, please check for any unknown applications that have been installed recently and uninstall them.