Microsoft has removed the ability to download files using Windows Defender. Users could run the Microsoft Antimalware Service Command Line Utility (MpCmdRun.exe) with the -DownloadFile argument. Microsoft has not said why this feature was added for an unknown reason. In tests, we were able to download any file, including ransomware, to our systems using the MpCmdRun command-line utility. We were shown how it could be used by attackers to download malware onto a computer. Microsoft told us, “Microsoft has nothing further to share”””
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-removes-windows-defender-ability-after-security-concerns/