I am having the same issue. Except its not JUST that one update. I've got FOUR Windows updates that downloaded and installed without my knowledge or permission. And I suspect I totally messed up another one today thinking I'd picked up a virus
My Windows Update settings are ALSO set to notify me when there's an update but NOT download or install without my permission. That hasn't changed, and when I "check for updates" it tells me that the last time I updated the computer was 7/24/2014 (which is what I remember). However when I actually look at the list of installed updates I see these:
Definition Update for Windows Defender - KB915597 (Definition 1.179.1033.0) Installation date: 7/25/2014 3:48 AM
Definition Update for Windows Defender - KB915597 (Definition 1.179.1461.0) Installation date: 7/29/2014 3:49 AM
Windows Update Agent 7.6.7600.320 Installation date: 7/31/2014 6:18 PM
Definition Update for Windows Defender - KB915597 (Definition 1.179.1796.0) Installation date: 8/1/2014 3:48 AM
And then this afternoon, my computer suddenly forced a reboot, and on reboot began installing updates, and I FREAKED thinking I'd picked up a virus, interrupted the reboot/install, forced it into safemode, ran a virus scan, which came back clean, tried to restore to the restore point from the 24th only to discover that there'd been newer installs AND that because I'd interrupted the reboot/install I'd screwed up my computer.
If it had just been the one update to the updater I'd tolerate it, but its doing it with far more than that, and thats a problem.