The “Random Command Prompt Flash” Issue

If you’re using Windows 10 and Office 365, you might have noticed a strange issue: for the past six weeks or so, some users have reported command-prompt windows popping up for a fraction of a second, seemingly at random. This issue may affect computers running Windows 7 or 8.x and\or Office 2016, but so far I have only seen the issue on computers running Windows 10 and Office 365.

I noticed the issue on my own computer a couple weeks ago, after the latest Office 365 update. But the random command-prompt pop-ups didn’t happen immediately after the update, so I failed to connect the two. At first, I thought it might be some kind of malware, so ran scans using multiple products… which came back clean. I checked Event Viewer, but there were no obvious issues there. I looked at Task Scheduler, but nothing appeared to be amiss there, either.

Stumped, I downloaded and installed Open Broadcaster Software (OBS), an open source video capture tool. I closed all open apps, except for a single Chrome window, which I left open on a maximized nearly blank page. I set OBS to record my screen for two hours and walked away. I returned later and played the video back on my second monitor in VLC, with the playback speed cranked up to 4x. Sure enough, I eventually saw the command-prompt flash:

Office Handler window

If you can’t make out what title bar says, it’s

C:\Program Files (x86)\Microsoft Office\root\Office16\officebackgroundtaskhandler.exe

If you’re having this issue, you should be able to make the pop-up happen any time you want to by opening Task Scheduler and going to Library > Microsoft > Office, right-clicking on

OfficeBackgroundTaskHandlerRegistration

and choosing “Run”.

I don’t know how to “fix” this issue, and I assume Microsoft will address it in an upcoming Office 365 update. However, there is a workaround to prevent that damn command-prompt window from popping-up: right-click on the task and choose “Properties”. Click the “Change User or Group” button and change the user from “Users” to “System”. It’s not the most elegant solution (especially from a security perspective), but it works.

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