Microsoft has patched a zero-day bug in Windows Defender being actively exploited in the wild, as part of its monthly update round. The first Patch Tuesday of 2021 featured fixes for 83 vulnerabilities in Windows OS, Edge, Office, Visual Studio, .Net Core, .Net Repository, ASP .Net, Azure, Malware Protection Engine and SQL Server. Remote code execution bug CVE-2021-1647 is the most urgent, according to Chris Goettl, director of product management for security products at Ivanti. He recommended organizations ensure their Microsoft Malware Protection Engine is version 1.1.17700.4 or higher. “Microsoft frequently updates malware definitions and the malware protection engine and has already pushed the update to resolve the vulnerability,” Goettl explained.