Microsoft today is rolling out a new cumulative update for PCs and phones in the Release Preview ring of the Insider Program. KB3201845 brings the build number to 14393.479.
As usual, there is no changelog available, as Microsoft rarely offers release notes for cumulative updates that it ships to Insiders. If it does publish them, it only arrives after a day or two, and the company is yet to explain why it's so hard to offer release notes at the same time as it actually releases the build.
The new update will replace 14393.447 for PCs, and 14393.448 for Mobile, which were released about three weeks ago. If you're on the Production ring (non-Insiders), you're likely to see the new build in two weeks, which would be the December Patch Tuesday.
If Microsoft does find it in its heart to publish some kind of changelog of the build, it should show up in the Feedback Hub. We've reached out to the company to find out what it includes, and we'll keep you updated as we know more.