This is another "stabilization" build for the upcoming Fall Creators Update (due for release on 17th October) and as such contains just a few bug fixes. In this build those are:
- We fixed an issue some Insiders were experiencing where after upgrading to recent flights their optical drive wouldn’t be listed under This PC.
- We fixed an issue where Microsoft Edge might crash when scrolling embedded PDFs.
- We fixed an issue resulting in some Insiders seeing 0x80070005 when trying to upgrade to the last few flights.
- We fixed an issue where using the Automatic File Download notification to block an app from downloading files wasn’t working for UWP apps.
- We fixed an issue resulting in Windows Defender potentially downloading files selected to be online-only after using the file picker dialog and viewing their thumbnails
Here's the full release notes from Microsoft.