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Is it in Safaru ?
I see it is in Safari. That is a SCAM. Press Command, Option and Esc keys and this will bring Force Quit window. Select Safari and click Force Quit. This will close Safari.
Then hold down Shift key on your keyboard and open Safari. Click on Safari menu and select Clear History and Website Data. On the dropdown next to Clear, select All History and click Clear History.
(If you see Reset Safari instead, click it and Reset Safari)
That will remove it. Please let me know if that didn't work, so we can continue troubleshooting
Let me know if you are unable to remove it.