Microsoft has released an update for Windows Defender under Windows 10 that changes the Windows Defender Antimalware platform version.
Windows Defender Update KB4052623 has been released on January 19, 2018. Microsoft’s KB article KB4052623 isn’t updated yet, it’s dated January 5, 2018.
After updating, the Antimalware client version should be 4.12.17007.18011 under Windows 10 and Windows Server 2016 Version 1703 upward.