1. Check for adware.
Run the latest release of Malwarebytes for Mac to remove malware/adware, if installed on your Mac.
For instructions: Install Malwarebytes for Mac Uninstall Malwarebytes for Mac
Click the “Scan Now” button. Once done, quit Malwarebytes for Mac.
Restart the computer and relaunch Safari holding the shift key down.
Remove unknown profiles (1), unknown login items(@) unknown extensions(3), reset search engine (4)
and reset Homepage (5 & 6) listed under Additional steps.
2. Additional steps to take, if necessary.
1. Remove unknown profiles.
System Preferences > Profiles
Open System Preferences, click the “Profiles” icon ( a checkmark on a gear) .
When Profiles pane opens, select the unknown profile and click the minus button at the bottom.
2. Remove unknown Login item.
System Preferences > Users & Groups > Login items
Authenticate and unlock the lock.
Highlight the unknown login item and click the “-“ button at the bottom left to remove it.
3. Remove unknown extensions: Safari > Preferences > Extensions
https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac
4. Reset search engine: https://support.apple.com/guide/safari/customize-your-search-ibrwe75c2a3c/mac
Change Home Page
5. Reset Homepage. https://support.apple.com/guide/safari/set-your-homepage-ibrw1020/mac
Section: Check other browser settings.
6. Ref: https://forums.malwarebytes.com/topic/236261-how-to-remove-weknow-malware-and-others/
7. Shutdown the computer from menu. Start your Mac using the Power button.