safari, How to get rid of Marquis extension

Go step by step and test.

   1. Remove unknown profiles if present.

      System Preferences > Profiles

      Open System Preferences,  select “General and 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.

      Section: Remove a configuration profile from your Mac

      Profiles: Use configuration profiles to standardize settings on Mac computers - Apple Support

  2. Remove unknown extensions:  Safari > Preferences > Extensions

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

      Change Extensions preferences in Safari on Mac - Apple Support

   3. Check for adware.

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

       For instructions: For instructions:

          Install Malwarebytes for Mac v4                                                

          https://support.malwarebytes.com/hc/en-us/articles/360039025233-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.

  4. Reset search engine:    Customize searching in Safari on Mac - Apple Support

  5. Reset  Homepage.   Change your homepage in Safari on Mac - Apple Support 

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