Microsoft squashes data-eating bug in the Windows 10 October 2018 update

In the famous words of Homer Simpson, "doh!" That's probably the expletive most heard at Microsoft this past Saturday, when the company was forced to temporarily pull the Windows 10 October 2018 update due to a serious data-eating bug that would make users' documents vanish in a puff of bytes. The company has now identified the root cause of the problem and has since issued a fixed version of the update for Windows Insiders. The Windows blog also now has a detailed explanation of the issue up.

Some of the user reports about data loss pointed to user data folder redirection, known as Known Folder Redirection (KFR) in Microsoft parlance, and OneDrive as possible causes. Both theories were connected to the root cause. Since the April 2018 Update, some users that used KFR to redirect one of their data folders (Desktop, Documents, Pictures, etc.) reported an extra, empty copy on their systems. In what will soon be recognized as a case study of "best intentions gone wrong," Microsoft added code to remove those supposedly empty copies. You can work out what happened next.

Specific situations that would trigger the bug include redirecting a data folder to another drive without moving all the data in the process, redirecting data folders to One Drive without transferring the contents over, and using an older version of OneDrive with the auto-save feature enabled.

Microsoft says it'sĀ investigated the issue and fixed the bug in all three scenarios. Given the gravity of the bug, the Redmond folks are offering to assist customers in retrieving their data. The company will now monitor the situation "with the utmost vigilance" and will re-issue the October 2018 Update once it's sure that the data Pac-man isn't in it.

Tip: You can use the A/Z keys to walk threads.
View options