Virus
I believe this Mac has a Virus, this website search Maquis is there and yesterday had to delete a App claiming to be a cleaner think it was called Mac Booster but seemed unusual.
iMac 21.5″, macOS 10.15
It's not a virus. You installed it, which makes it a Trojan. The likely sources are a fake Flash popup you responded to, or you downloaded and installed software which included adware.
Download and run MalwareBytes for Mac. It's free to use and easily uninstalled from its menu option when you're done with it.