I don't think it was a Microsoft critical link but malware. Have a look in ad-ons and extentions, in Firefox, and disable or uninstall anything you don't recognise. Re-set your home page. Check programs and features for an unknown program and uninstall. Run Ccleaner's reg cleaner. Finally run Malwarebytes in safe mode then normal mode.
Amazon Fire HD 8 review: A brilliant combination of function and value – with one massive caveat