KitGuru published Microsoft will stop supporting Windows 10 Mobile security updates by the end of the year A quote from the article:

Back in 2017, Microsoft announced that its Windows 10 Mobile platform was entering its end-of-life support phase, scrapping plans for new hardware and features. Users continuing to use the obsolete operating system have now been notified that security updates will come to an end in December.

 Microsoft will stop supporting Windows 10 Mobile security updates by the end of the year