Microsoft released Windows 10 version 1511 build 10586.104, cumulative update 9 for version 1511, shipped as Windows Update KB 3135173. You can install it now (Start > Settings > Update & Security) or wait for it to install overnight.
Build 10586.104 contains a handful of fixes, including security patches, but that isn't the most important news.
Finally, for the first time, Microsoft has published a changelog for 10586.104. It doesn't have details of earlier cumulative updates, so we don't know what was changed before, but the changelog does have high-level descriptions of changes that were made in today's cumulative update. Microsoft says:
We're committed to our customers and strive to incorporate their feedback, both in how we deliver Windows as a service and the info we provide about Windows 10. In response to this feedback, we're providing more details about the Windows 10 updates we deliver through Windows Update. You'll see a summary of important product developments included in each update, with links to more details. This page will be regularly refreshed, as new updates are released.
That, my friends, is a breath of fresh air. It addresses my biggest beef in the 10 hurdles to Windows 10 adoption slideshow -- one of the most widely read articles I've ever written. Someone, it seems, is listening.
The changelog tells us, for example, that this build should fix the embarrassing bug in Microsoft Edge, where the browser stored historic lists of visited URLs while running in InPrivate mode. Security researcher Brent Muir first identified that security leak last September.
The changelog also has a link to KB 3135173 itself, which should give us more details on the security holes being patched, and their associated Security Bulletins. (The KB article isn't available as we went to press, but it'll be up sooner or later.)
I've installed and used 10586.104 for a total of about 10 minutes and don't see any immediate problems. It's still much too early to say it's relatively problem-free, so those of you using various methods to delay Windows 10 patches should hold off for a few days. But as it stands now, we're looking at a major shift in Microsoft transparency.