In addition to redelivering Windows 10 1809 today, Microsoft is also beginning the rollout of the initial release of its monthly cumulative updates for Windows 10. The company regularly releases its first round of updates on the second Tuesday of each month, and the delivers subsequent updates during the rest of the month to solve issues introduced by the first round.
As we recently reported, there’s a known file extension bug that Microsoft is still working to resolve. Some have incorrectly reported that it would be fixed today, but as we reported, Microsoft is working to resolve this later in the month.
The Windows Update History page for each Windows 10 version confirms it:
After installing this update, some users cannot set Win32 program defaults for certain app and file type combinations using the Open with… command or Settings > Apps > Default apps.
In some cases, Microsoft Notepad or other Win32 programs cannot be set as the default.
In some cases, attempting to set application defaults again will succeed.
Microsoft is working on a resolution and estimates a solution will be available in late November 2018.
Fortunately, this bug only affects two versions of Windows 10. But, unfortunately, its the latest versions that are affected.