Microsoft Security Essentials (MSE) will continue to receive definition updates for new malware after Windows 7 reaches End of Support, even though a Microsoft support bulletin states otherwise. Microsoft Employee Mike Cure said that MSE would still get signature updates after January 14th, 2020. While this is surely good news for MSE users on Windows 7, it still does not mean you should continue to use Windows 7 or MSE for that matter. Without a subscription to Windows 7 extended security updates, using the unsupported operating system will open users to vulnerabilities that will no longer be fixed.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-security-essentials-to-get-updates-after-windows-7-eos/