I haven't used macOS since the Panther days so I don't feel confident walking you through step-by-step however I found a guide *https://www.securemacos.com/single-post/2016/09/09/Remove-safefinder-virus-from-Apple-Mac-OS-X

Where does Safe Finder show up? Here are some resources to help you root it out: * Start page: check your home page setting and extensions * Search results: check your default search setting and extensions * New tab page: check your extensions And now, the details: I suggest starting with an extension check. You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either: * Command+Shift+a (Windows: Ctrl+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 that Firefox installs on its own are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious? If in doubt, disable. Often a link will appear above at least one disabled extension to restart Firefox before the change takes effect. You can complete your work on the tab and click one of the links as the last step. Any improvement? '''Home page and search''' * [[Startup, home page, tabs, and download settings]] * [[How to set the home page]] * [[Change your default search settings in Firefox]] Success?