Last week we paused the rollout of the Windows 10 October 2018 Update (version 1809) for all users as we investigated isolated reports of users missing files after updating. Given the serious nature of any data loss, we took the added precaution of pulling all 1809 media across all channels, including Windows Server 2019 and IoT equivalents. We intentionally start each feature update rollout slowly, closely monitoring feedback before offering the update more broadly. In this case the update was only available to those who manually clicked on “check for updates” in Windows settings. At just two days into the rollout when we paused, the number of customers taking the October 2018 Update was limited. While the reports of actual data loss are few (one one-hundredth of one percent of version 1809 installs), any data loss is serious.

We have fully investigated all reports of data loss, identified and fixed all known issues in the update, and conducted internal validation. Also, Microsoft Support and our retail stores customer service personnel are available at no charge to help customers. More details are available below.

Today we take the next step towards the re-release of the Windows 10 October 2018 Update by providing the updated version to our Windows Insider community. We will carefully study the results, feedback, and diagnostic data from our Insiders before taking additional steps towards re-releasing more broadly.

More Information

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\<folder name>, 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.

Today, we also released some other fixes in the monthly update for customers who have already taken the Windows 10 October 2018 Update. More details are available in KB 4464330.

Support for affected users

To help our customers that may be impacted by this issue, Microsoft Support is assisting customers and trying to recover data for users who may have experienced related data loss. Microsoft retail stores support services also offer this same level of support in-store. While we cannot guarantee the outcome of any file recovery work, if you have manually checked for updates and believe you have an issue with missing files, please minimize your use of the affected device and contact us directly at +1-800-MICROSOFT or find a local number in your area. For more information, please refer to our Windows 10 update history page (KB article), which we are updating with new information as it is available.

Next Steps

To help us better detect issues like this, today we have enabled a new feature in the Windows Insider Feedback Hub. We have added an ability for users to also provide an indication of impact and severity when filing User Initiated Feedback. We expect this will allow us to better monitor the most impactful issues even when feedback volume is low.

We will continue to closely monitor the update and all related feedback and diagnostic data from our Windows Insider community with the utmost vigilance. Once we have confirmation that there is no further impact we will move towards an official re-release of the Windows 10 October 2018 Update. We apologize for any impact these issues may have had on any of our customers. We are committed to learning from this experience and improving our processes and notification systems to help ensure our customers have a positive experience with our update process.