Update 10-October: Microsoft says it has identified the underlying cause of the data deletion bug and has begun rolling out a fix, starting with members of the Windows Insider Program. For details, see "Windows 10 October 2018 Update: Microsoft releases fix for data deletion bug."
Microsoft has halted the rollout of Windows 10 version 1809, the October 2018 Update. The company released its latest feature update to the general public on Tuesday, October 2nd, and had planned to begin delivering it automatically through Windows Update roughly a week later. Those plans are on hold while the company investigates reports of data loss associated with this upgrade.
Also: Microsoft pulls Windows 10 October Update (version 1809)
Earlier today, on its Windows 10 Update History page, Microsoft confirmed its decision to suspend the public delivery of this version:
We have paused the rollout of the Windows 10 October 2018 Update (version 1809) for all users as we investigate isolated reports of users missing some files after updating.
If you have manually downloaded the Windows 10 October 2018 Update installation media, please don't install it and wait until new media is available.
We will provide an update when we resume rolling out the Windows 10 October 2018 Update to customers.
Via email, a Microsoft spokesperson confirmed that announcement: "We have paused the rollout of the update while we continue to investigate reports from some customers."
In a tweet, Dona Sarkar, who runs the Windows Insider Program, advised anyone affected by this issue to call Microsoft's support lines: "They have the tools to get you back to a good state." The implication in that tweet (and in the language from the original bulletin) is that the files have not been deleted but are available elsewhere on the system disk.
Update: Roughly 36 hours after the initial publication of the support bulletin, Microsoft edited its contents. It now reads, "If you have manually checked for updates and believe you have an issue with missing files after an update, please minimize your use of the affected device and contact us directly..." [emphasis added]
In the United States, you can reach Microsoft Support at 1-800-MICROSOFT (1-800-642-7676). For Windows 10 customers in other regions, check the list of local support numbers on the Global Customer Service Phone Numbers page.
This is the second straight semi-annual release that has been plagued by isolated reliability problems at the time of rollout. The April 2018 Update (version 1803) just barely made its official release month, with Microsoft giving it the green light on April 30. Even then, the initial release had some noteworthy problems caused by compatibility issues with Avast antivirus software and disk drivers for some SSDs.
In November 2015, Microsoft pulled the first Windows 10 feature update (version 1511) from its download servers unexpectedly, but didn't do so in response to any known bugs.
As ZDNet's Liam Tung reported earlier this week, the first wave of reports came from Reddit, Twitter and Microsoft's Community forums.
This morning, I searched through Microsoft's Feedback Hub app, where Windows 10 users can provide bug reports and feature requests for both previews and released builds. A quick search revealed multiple examples of users reporting issues with deleted files.
One report from three months ago was headed "Files deleted!!!!" and noted that after installing a preview release "my Documents folder had been overwritten with a new Documents folder, complete with custom icon. All contents were gone."
A more recent report was filed by a Windows 10 user who installed the version 1809 update within hours of its release:
Upgraded Dell Inspiron from April 2018 to October 2018, and all my documents and photos were deleted. This occurred on only this laptop; one Acer laptop and two desktops upgraded at the same time did not experience this.
On the Inspiron, only docs and pictures on my account folder were lost; other user account documents and photos on this laptop were fine.
Multiple replies cited similar experiences, all within 48 hours of the original report:
I'm on a Dell Precision. This happened to me as well! The contents of the Documents folder totally disappeared. All the other folders for my user profile such as Desktop, AppData, etc are intact. Fortunately I had a backup from the summer. I have been a loyal Windows user since Win95, and I've never had a Windows update single out my Documents folder for deletion. Very disappointed today.
Several commenters who updated multiple machines have reported that the issue affected only one device:
I have had the same issue happen. I updated two computers last night. One computer Documents and Pictures are there and everything is good on the second computer my Documents and Pictures folder is now empty, all files that where in these folders are gone. I can confirm that the other files in my Users folder are still there, it appears that only Documents and Pictures where deleted.
Another Windows Insider Program member who filed feedback reported experiencing issues on one PC, while three other upgraded devices were unaffected. That report noted that only the Documents folder was deleted, leaving the Downloads, Music, and Favorites folders undisturbed.
After manually scanning multiple public Feedback Hub reports, I can't find any obvious patterns. One feature that I am suspicious of is the new Auto Save capability added to OneDrive earlier this summer, which allows Windows 10 users to link the local Documents, Pictures, and Desktop folders. (See "Microsoft brings 'Known Folder Migration' feature to OneDrive consumer users.")
Microsoft claims that so far this issue involves "isolated reports." That is probably accurate. At this point in the rollout cycle a very small number of devices (no more than a few million), are running Windows 10 version 1809. All of those upgrades should have been delivered either to members of the Windows Insider Program or to what Microsoft calls "seekers," who proactively visited the Windows 10 download page to install the upgrade manually.
(That, of course, assumes that Microsoft has stuck to its previously announced schedule. I have heard from one colleague who received the new feature update automatically on a device that is not registered with the Windows Insider Program. That would be several days ahead of the announced release for automatic updates.)
Because the problem appears to be associated with the data migration portion of Windows Setup, it's unlikely that it will affect you if you've already successfully upgraded to this feature update. If you previously downloaded the installation media and were considering a manual upgrade this weekend, you'd be well advised to cancel those plans.
For PCs running Windows 10 Pro or Enterprise, version 1803, I strongly recommend using one of the techniques in this article to defer this feature update until these initial issues have been fully resolved:
Windows 10 October 2018 Update: How to get it, how to avoid it
At a bare minimum, I recommend moving any business PCs to the Semi-Annual Channel from the default Semi-Annual Channel (Targeted).
Meanwhile, this situation underscores the need to have comprehensive local and cloud-based backups. This specific bug is only one entry on the nearly infinite list of Things That Can Go Wrong With Storage Devices. The unfortunate soul who reported losing 220 GB of data, for example, could have saved himself a great deal of heartache by archiving those folders to OneDrive, Dropbox, Google Drive, or another cloud storage service and then using Windows 10's built-in File History tool to back up data files.
Also: Windows 10 tip: Turn on File History for automatic backups
Regardless of your operating system, now might be a good time to check your backups.
Previous and related coverage:
Is speedy rollout of Windows 10 version 1803 causing quality problems?
Microsoft insists that its rollout of the latest Windows 10 feature update is going well, but some customers are skeptical. And without accurate data, it's impossible to tell who's right.
Windows 10 October update problems: Wiped docs, plus Intel driver warning
Back up files before upgrading to Windows 10 1809, and if you get a warning about Intel drivers, do not proceed.
Windows 10 tip: Turn on File History for automatic backups
Windows 10's File History feature keeps regular copies of files so you can roll back to a previous version of a file or restore an entire system. The feature is designed to use an external drive, but you can also specify a network location. Here's how.
Windows 10 October 2018 Update: How to get it, how to avoid it
Microsoft will soon begin delivering the official release of Windows 10 version 1809, the October 2018 Update. If you do nothing, it will arrive via Windows Update some time in the next few months. Here's how to take more control over the process.