How do I stop the yahoo redirect?

 1. Use  the latest release of MalwareBytes for Mac to remove malware/adware.

     Install guide:       https://support.malwarebytes.com/docs/DOC-1817

     Uninstall Guide:  https://support.malwarebytes.com/docs/DOC-1190

     The installer may ask you to allow it in Security & Privacy  /System Preference. Allow it.

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

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

2. Additional steps to take if necessary.

   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.

  Remove unknown extensions: https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac

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

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

Did you uninstall/remove unknown extensions as an additional step?

  Remove unknown extensions: https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac

If this doesn't help:

      Download EtreCheck: https://etrecheck.com/maspro  and post the report here.

      Click, “Free Download” button and then  “Click to download” button,

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

      Click on the bouncing  EtreCheck icon in the Dock.

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

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

      Paste the report when you reply.

Yahoo redirect - Please do a manual uninstall and do not download anything but Malwarebytes.

See if the below helps. I would scroll down to the below or you might fall asleep.

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• Step 1. Eliminate Yahoo Redirect from Windows
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• Step 2. Delete Yahoo Redirect from Mac OS X
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• Step 3. Uninstall Yahoo Redirect from Internet Explorer
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• Step 4. Remove Yahoo Redirect from Microsoft Edge
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• Step 5. Erase Yahoo Redirect from Mozilla Firefox
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• Step 6. Get rid of Yahoo Redirect from Google Chrome
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• Step 7. Eliminate Yahoo Redirect from Safari
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https://www.2-spyware.com/remove-yahoo-redirect-virus.html