The FBI has observed cybercriminals targeting computer network infrastructure after an operating system achieves end of life status. Windows 7 no longer receives free software updates and security updates or fixes unless customers get an Extended Security Update (ESU) program subscription. Microsoft says that upgrading to Windows 10 from Windows 7 for free was only available until July 29, 2016, free Windows 10 upgrades are still a thing if you follow this step by step Windows 10 upgrade procedure that involves running the Media Creation Tool and choosing the ‘Upgrade this PC now’ option on Windows 7 computers.
Source: https://www.bleepingcomputer.com/news/security/fbi-networks-exposed-to-attacks-due-to-windows-7-end-of-life/