[WindowsCentral.com]

Do you see a Command Prompt box flash quickly on Windows 10? It's Office 365 fault. There is a fix coming, but here's what you can do now.

If you recently started noticing a Command Prompt box flashing quickly every hour on your Windows 10 computer, you should know that it's not a virus or malware trying to steal your information. It's actually a bug with Microsoft Office 365.
The anomaly is caused by two tasks, including OfficeBackgroundTaskHandlerRegistration and OfficeBackgroundTaskHandlerLogon that Office 365 automatically configures with the Task Scheduler on Task Scheduler Library > Microsoft > Office. And every time they run, they cause a window to appear quickly in the screen every hour, and every time you sign in to Windows 10. However, this is not an issue affecting everyone; it only seems to be happening for those users who are enrolled in the Fast ring of the Office Insider Program.

Full story from the WindowsCentral blog...