Microsoft Office: Command Prompt window flashes every hour

It is current year, and Microsoft lets loose a bug like this in its flagship application.

There's no option but to keep Office up to date. It is not written in Rust, so it's afflicted by memory safety issues, so it needs to be updated as they are discovered. Otherwise, the computer is vulnerable to exploits. Even then you are still vulnerable, because there are unknown defects. But keeping a program like this up to date is not optional.

So I recently updated Office, and this weird window starts appearing on my screen. Whatever I'm doing - reading emails, developing, browsing - every once in a while a black console window would briefly appear. It would steal focus from what I'm doing, and close too fast to see what it is.

How to debug this?

I tried Process Monitor. This is an awesome tool, but somewhat unreliable. I hoped to keep it running to capture the Process Start event to identify the rogue window when it pops up, but it's not stable enough to keep running for hours.

So I opened Notepad and started writing down the times when I noticed the window.
Ah, that's a clear pattern.

Next day, I set an alarm to 11:35 to remind me to start Process Monitor just before I expect the window to appear. And there it is:

This is now enough to do a web search, and it turns out this is a problem people have been reporting since at least April 14 on the Office "Insider Fast" track.

Despite people reporting this problem, it has made it to release.

The pop-up is being run from the Windows Task Scheduler, using this task:

Microsoft > Office > OfficeBackgroundTaskHandlerRegistration

This runs a program named OfficeBackgroundTaskHandler.exe, which is a small program that seems to do approximately nothing. Except when it does something. Who knows?

It is possible to disable this task. What are the side effects of disabling it? I don't know.

It is possible to make it run as the SYSTEM account. The task will then run, and the pop-up will be hidden. But does the task still do its job properly then? What are the security risks of running it as SYSTEM?

It is disappointing that this issue made it live, and more so that it is apparently not a priority.

It's not that surprising, though. The pop-up annoys everyone, but few can find out what it is.

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