Yesterday Apple released a security update for Mac that you should download and install immediately. To be brief, it closes a hole that allows a user to bypass Administrator authentication without using the Administrator password. The download isn't very big, so it won't take too much time out of your day to update your system.
It appears that a security update for the CVE-2019-1402 vulnerability in each version of Microsoft Office causes this error. Here is the list of Office security updates that you can uninstall.
Office 2010: Description of the security update for Office 2010: November 12, 2019 (KB4484127)
Office 2013: Description of the security update for Office 2013: November 12, 2019 (KB4484119)
Office 2016: Description of the security update for Office 2016: November 12, 2019 (KB4484113)