As I wrote in my posting, your are not able to stop the process (unless you are using the enterprise version).
As I further wrote in my posting, I first thought, that a security update has caused the problem (and uninstalled all the security updates first). The security updates then were reinstalled automatically again.
But it seems as "normal" updates (like the problem-update KB3114717) aren't reinstalled, if removed manually (at least not by every reboot - I hope never, but don't know for sure) .
Update:
The KB3114717 was installed again ("in the background") without reboot!
=> So yes @MS:
- How to prevent the reinstall?!! - When do you apply a bugfix, so that your customers worldwide are able to work again with Office?!