Microsoft released the Windows 10 October 2018 Update earlier this month to introduce a smorgasbord of new features. The update had a critical flaw that deleted user files, however, so the company pulled it shortly after its debut. (The update is also said to have caused problems with Intel audio drivers, but that issue wasn't nearly as serious.) Now the flaw has been fixed and the latest version of Windows 10 is available once more.
Microsoft decided to re-release the Windows 10 October 2018 Update to members of the Windows Insider Program first. That makes sense--people used to using pre-release software are more likely to accept the risk of data loss. The company said it will "carefully study the results, feedback, and diagnostic data from our Insiders before taking additional steps towards re-releasing more broadly."
Here's how Microsoft explained the cause of the problem:
"[File loss] 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."
This led to three potential issues; Microsoft said it's fixed all of them. It also released some other small updates: a fix to a bug that deleted user profiles due to incorrect time calculation if the "Delete user profiles older than a specified number of day” group policy is enabled; and security updates for everything from the Windows Kernel and Windows Media Player. (And Internet Explorer, which is actually listed twice.)
Microsoft noted that this issue didn't affect many people. Microsoft said the problem with the Windows 10 October 2018 Update affected "one one-hundredth of one percent" of people who installed the update before it was pulled. Given that the company hadn't even officially released the update, and people had to go searching for it online if they wanted to install it, that means the vast majority of Windows 10 users were just fine.
But nobody wants to lose their files because of a flaw with an operating system update, so Microsoft likely made the right choice in pulling the Windows 10 October 2018 update instead of gambling with data from "one one-hundredth of one percent" of Windows 10 users. We'll see how well the problem was addressed--and what other flaws are waiting to be discovered--once the update is officially released to the public again.