Safari redirects to yahoo

   1. Remove adware if installed on your Mac.

       Run the latest release of Malwarebytes for Mac to remove malware/adware, if installed on your Mac.

       For instructions: Install Malwarebytes for Mac v4      Uninstall Malwarebytes for Mac

       Click the “FREE DOWNLOAD” button.

       Click the “Scan ” button. Once done, quit Malwarebytes for Mac.

       Restart the computer and relaunch Safari holding the shift key down.

       Scan for Malware again.

       Additional steps  if necessary.

  2. Reset search engine:    https://support.apple.com/guide/safari/customize-your-search-ibrwe75c2a3c/mac

  3. Reset  Homepage.   https://support.apple.com/guide/safari/set-your-homepage-ibrw1020/mac 

  4. Remove unknown extensions:  Safari > Preferences > Extensions

      https://support.apple.com/guide/safari/use-safari-exthttps://etrecheck.com

      If this doesn’t help, download EtreCheck..

      https://etrecheck.com

      Click  “Free download” button,

      Open Downloads folder, click on it to open, and then select ”Open”.

      “Choose a problem” from the popup menu box, and then “Start EtreCheck” in the dialog.

      Click “Share Report” button in the toolbar, select “Copy report” .

      Paste the report when you reply.