installed Defender a few days and appears to be running normally, not
experienced any problems but do see a message pop up from the taskbar shortly
after startup.

message reads...

"an application registration change was made for a known application file:
C:\Program Files\Windows Defender\MpCmdRun.exe"

it appears briefly then closes.

is this normal? what does it mean?

Hello RCW2005,

MpCmdRun.exe monitors for the existence of new signatures and is responsible
initiating the updating process when new signatures are available. ...

I hope this post is helpful.
Еиçеl
--
"RCW2005" wrote:

> installed Defender a few days and appears to be running normally, not
> experienced any problems but do see a message pop up from the taskbar shortly
> after startup.
>
> message reads...
>
> "an application registration change was made for a known application file:
> C:\Program Files\Windows Defender\MpCmdRun.exe"
>
> it appears briefly then closes.
>
> is this normal? what does it mean?