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.
How to get Windows 10 now: how to download and install Windows 10 even if GWX.exe is missing