Windows Defender Update failing

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Let me give it a try. C:\Windows\Temp contains MpCmdRun.log and MpSigStub.log files which can give us more knowledge about the error happening with Defender.

After watching your logs, I found I saw a similar case (though that was of Windows 8.1) and the problem was resolved by this:

Stop Windows Update service, clear C:\Windows\Temp and %UserProfile%\AppData\Local\Temp (and clear SoftwareDistribution folder also), restart Windows Update service and try updating Windows Defender again.

If we clear those two temp folders we will lose the logs, so first copy them somewhere else (MpCmdRun.log file is also in User's Temp) and then try it.

Prashant Kumar