Seen this on two Windows 10 desktops today. Flashes by too quick to tell it is a command prompt (just the outline of a window flashes on the screen) but it is the right size for one.
Scans are clean and it fits with a task in task scheduler that I think may have been added/modified by a recent Office upgrade.
The task is named
This is all speculation so far but wanted to add that I too have had it reported to me by users and this is what I have found in common so far.
EDIT: Found more info about this...
"This issue is fixed starting with build 16.0.8201.2025 which is now available as the latest update for those participating in the Office Insiders Slow program. It will be included in a future update for those not participating in Insiders."
So if that is indeed our issue it should be fixed in an update soon.
I can actual confirm that this appears to be the issue that occurred for me. I noticed that the command prompt was opening almost precisely every hour, so I was able to take a screen shot:
You can see that most of the word OfficeBackgroundTaskHandlerRegistration is in the titlebar. I also found this to questions saying this is the issue, from a few days ago.
Although I have not had my computer on for longer than an hour after reading the answer, to confirm if the fix works, the below is the suggested method to stop the propmt from popping up.
Method to Stop Command Prompt Pop-Up:
Go to the Task Scheduler then disable the task OfficeBackgroundTaskHandlerRegistration in the task scheduler. To get to that task, in the left pane find the Office folder (located under Task Scheduler Library > Microsoft)
I go the answer from this thread on Reddit.
I suppose when the issue is eventually patched you can re-enable the OfficeBackgroundTaskHandlerRegistration task if it's needed and obviously, if the disabling the task causes you issues then enable it again, but the pop-up will return. (I haven't run into any issues yet with the task disabled though).
Edited by Lxno78, 30 May 2017 - 06:20 PM.