That updater app is installed by most Microsoft software, such as Microsoft Office.
Should be located in the usual location: /Library/ApplicationSupport/Microsoft/MAU2/
That will help you find the Microsoft Autoupdate app. If you have any other Microsoft apps installed, you can just leave it (Hit the update button there, which would fix the immediate issue), or, no Microsoft apps, don't use any MS, drag the app to the trash and empty the trash...