This is a program that is part of every Windows Update (I've seen it since Windows XP at least).
As far as I can see it runs at the time of the update. I believe it is intended to check and clean-up with regard to malware issues that could affect the updates. I've never seen it pick up anything - but that could just be due to the PCs being clean in the first place.
Safe to let it run and it will take quite a few minutes (especially on older machines).