Windows settings update problemInstallation Failure: Windows failed to install the following update with error 0x80070643: Definition Update for Windows Defender - KB2267602 (Definition 1.239.701.0).

Same issue, started after Cumulative Update for Windows 10 Version 1703 for x64-based Systems (KB4016250) installed. I have to manually download definition updates from

https://www.microsoft.com/security/portal/definitions/adl.aspx 

Same here, no matter what I do I cannot get defender to update.

Hi All,

Thank you for your patience regarding Windows Defender update error 0x80070643. We are aware of the issue and trying to roll out a mitigation as soon as possible. Meanwhile to get your machine back to a protected state, you can manually download and apply the latest Definition Update by following the instructions outline here: https://www.microsoft.com/security/portal/definitions/adl.aspx.”

This problem is not just limited to Insider builds I should add. I have checked several computers and the error occurs even on version 1607, which is the version on consumer computers!

How many non tech users are now being left vulnerable because of this mess up. Also how many will do manual updates?

Should we all start asking for refunds on what seems a faulty product I wonder? Defender gets plugged by you guys as the ideal answer and now the thing fails to work as it should and how many in-tech users are being left at risk?

As it affects the present v1607 used by millions I would have thought this problem would have a much higher concern for the tech staff at Microsoft? Why are you not concerned that many non-tech users may be left at risk on their computers?

Also I ran the windows update troubleshooter & it 's result is that it finds and fixes everything

but still does not change results of checking update error

I just hope a fix can be released soon as I have no way of knowing if Windows system updates are not going to install.

It is even a problem on the non-Insider versions too (v1607) so sounds like Microsoft has a big problem to sort ASAP

Even after a manual update as Microsoft suggest it still shows as a failed update so like you I wonder if it even works...

This happens even on version 1607! This was after I did a manual update as you suggest. Is Windows Defender even reliable at the moment????