Microsoft released the Windows 10 October 2018 Update on October 2nd, but then quickly pulled it from access (it had not started rolling out, but was made available to non-Insiders via Windows Update). The problem was supposedly a bug that was deleting users' Documents folders in rare but devastating cases, an issue that had been around for at least some of the RS5 development cycle according to entries in the Feedback Hub, but slipped through the cracks, apparently. It wasn't until some tech pundits noticed Reddit complaints that Microsoft took notice.
A fix has been issued, and is now in testing via Windows Insiders, and was also pushed to those who did download from Windows Update. Much has been made about how a more robust (non Pumpkin Spice) Release Preview Ring could have flagged the problem before letting it loose in the wild, but the occurrences were rare, so while it's possible, it's also possible that Release Preview complaints would have been missed, too.
But the real problem here is that these missing Documents folders weren't a bug at all, the functionality was introduced into RS5 builds *by design*. First, let's take a look at what Director of Program Management for Windows Servicing and Delivery said about the problem, in full:
Prior to re-releasing the October 2018 Update our engineering investigation determined that a very small number of users lost files during the October 2018 Update. This occurred if Known Folder Redirection (KFR) had been previously enabled, but files remain in the original “old” folder location vs being moved to the new, redirected location. KFR is the process of redirecting the known folders of Windows including Desktop, Documents, Pictures, Screenshots, Videos, Camera Roll, etc. from the default folder location, c:\users\username\, to a new folder location. In previous feedback from the Windows 10 April 2018 Update, users with KFR reported an extra, empty copy of Known Folders on their device. Based on feedback from users, we introduced code in the October 2018 Update to remove these empty, duplicate known folders. That change, combined with another change to the update construction sequence, resulted in the deletion of the original “old” folder locations and their content, leaving only the new “active” folder intact. Accordingly, below are the issues we have identified and fixed:
- Using KFR the user redirected a known folder to a different drive. For example, suppose you ran out of space on your C drive. You want to save some files separate from your primary folder, so you add another drive to your system for these. You create “D:\documents” and change the location of the files known folder from the original “old” location c:\users\username\documents to D:\documents. In some cases, if the contents of c:\users\username\documents were not moved to D:\documents, then a user could also encounter this issue. When the October 2018 Update was installed the original “old” folder was deleted including the files in that folder (in this example c:\users\username\documents would be deleted; d:\documents, the new location, would be preserved).
- The user configured one or more of their Known Folders (Desktop, Documents, Pictures, Screenshots, Videos, Camera Roll, etc.) to be redirected (KFR) to another folder on OneDrive. For example, the user changed the location property of the documents folder from c:\users\username\documents to another folder. During this process the system prompts the user and asks if they would like to move the files to the new location. If the files were not moved and the October 2018 Update is installed the original “old” folder was deleted including the files in that folder.
- The user used an early version of the OneDrive client and used the OneDrive settings to turn on the Auto save feature. This feature turned on KFR for the Documents and/or Pictures folders based on the user’s choice but did not move the existing files from the original “old” location to the new location. For example, if a user turned on Auto Save for pictures the location of the Pictures folder would be changed from c:\users\username\pictures to c:\users\username\onedrive\pictures, but no files would be moved. The current version of this feature moves the files. If the files were not moved and the October 2018 Update was installed the original “old” folder was deleted including the files in that folder (in this example c:\users\username\pictures would be deleted; c:\users\username\onedrive\pictures, the new location, would be preserved).
We have fully investigated these issues and developed solutions that resolve all three of these scenarios, so the “original” old folder location and its contents remain intact.
So at some point, Microsoft decided to go ahead and delete your original \user\<username>\documents or \pictures for you if you had used KFR, without any confirmation or knowledge on your part. This was not a bug, it was a conscious decision on Microsoft's part to delete user folders without confirmation by the user. Making matters even worse, the probable most likely scenario for lost files would be the third one, where OneDrive previously set a new autosave location, while leaving the old Pictures folder intact, and full of pictures before the OneDrive change. They decided, again by design (either that or one hand doesn't know what the other hand is doing or has done, so much for the end of old siloed Microsoft), to delete the folder anyway.
How could Microsoft not know of this OneDrive behavior? How could they build a system that didn't check if the folders were empty? How could they not alert users and ask explicit permission before deleting user folders, empty or not? Why weren't Insiders not told about these changes and asked to test them?
Maybe instead of requiring Windows Insiders to rate the severity of their bugs, Microsoft should let users know when they're messing with user content. The mind reels at the stupidity of these decisions, and Microsoft is just lucky that more people weren't affected.