In a recent blog post-Microsoft introduced many to its “C” and “D” releases (see: Windows monthly security and quality updates overview). These releases are essentially for those tasked with testing updates for their company. Included in these updates are non-security components that will show up in the next Patch Tuesday full update (Microsoft labels this as the “B” release). Normal users – or, for clarity, those that don’t manually check for updates – will never see the “C” and “D” releases. Only those that go into Settings > Update & Security > Windows Update and click the “Check for updates” box will be presented with these particular updates.
So, essentially, if you don’t want to be a guinea pig for updates, don’t manually check for updates. Manually checking for updates, opts you into beta testing Patch Tuesday updates and can have a negative impact.
However, despite the attempt at clarity, Microsoft missed a couple points in the blog post. Particularly, customers wondered how these updates were considered “optional” and why anyone would want to install them.
Microsoft’s John Wilcox says this…
You are correct, with Windows 10, all releases, Quality and Feature are cumulative, so subsequent releases are built on and contain all previous releases.
To minimize end-user reboot disruption, most of our self managed customers, and as default for the devices we manage, configure to update once a month, to get the latest security patches. These are the B releases.
We refer to the “C” and “D” releases as “optional” because”
- They only include quality fixes, not security fixes and therefore don’t have the zero-day exposure implications.
- The fixes will come to you in the next “B” release, which is what we and most of you are focused on getting quickly installed when they come out. So unless there is a specific fix that you’re blocked on, and thus need quickly, you will get the improvements with the next “B”, along with the new security fixes, and then only have on reboot.
“C” and “D” are there too so that if you want, you can deploy them early with your first flighting rings and have data and visibility to the changes before deploying the “B” release.
The fixes themselves are not optional, as you correctly called out, we only have cumulative updates now, but the specific update package that you deploy to get a set of fixes, and when is optional.