Virus on safari

In addition to the above, go to Safari Preferences/Extensions, uninstall any you don't recognize, and then turn all extensions off. Test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.

 Safari/Preferences/General - see what the Home Page is set to. If something you don't recognize, see if you can replace it with something you want.

 Safari menu/Clear History.

 System Preferences and remove any Profiles you see.

Install Malwarebytes and let it look for adware/malware which is most likely redirecting Safari to Yahoo. Do not subscribe, and when you are done, you can uninstall Malwarebytes from its Help menu. Reboot your Mac.

Following the anti-virus vendors uninstall instructions, remove it from your Mac. There are no viruses on Mac for it to detect, and no Windows viruses can run on a Mac anyway.

If you adopt a policy of only downloading software from the original vendor site, and not from anywhere else, adware and malware will become nearly extinct on your Mac.