Microsoft has fixed a bug in its latest Windows 10 October 2018 update that deleted files en masse for some users.
The software giant was forced to pull the update over the weekend due to the data deletion issues.
Now, the update is back online, but Microsoft says it is only releasing it to members of the Windows Insider program before making it available to the general public.
‘We have fully investigated all reports of data loss, identified and fixed all known issues in the update, and conducted an internal validation,’ John Cable, Microsoft’s director of program management for Windows servicing and delivery.
‘…We will carefully study the results, feedback, and diagnostic data from our Insiders before taking additional steps towards re-releasing more broadly.’
Cable said the mass-deletion bug only affected a small number of users – specifically those who had manually turned on the ‘check for updates’ feature in advance of the update’s wider release.
The update was then taken offline just two days after it was launched.
Microsoft estimates that the number of users affected amounted to one one-hundredth of a percent of installs, but still regards the data loss as ‘serious.’
However, ZDNet estimates that several hundred people are likely to have lost their files.
The firm believes the bug may have been tied to a feature called Known Folder Redirection.
Known Folder Redirection allows users to redirect folders such as documents, desktop and pictures from the default location.
Microsoft introduced code in the 2018 update to remove these empty and duplicate known folders, but in some cases, there was still some data leftover in the folders.
Microsoft said the bug only affected a small number of users – specifically those who had manually turned on the ‘check for updates’ feature in advance of the update’s wider release
Now, with the Windows 10 2018 reissue, the firm says it has included a patch.
‘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,’ Cable explained.
The firm said it received user reports of the bug early on, but didn’t take action because the total number of reports was too low to be flagged by its engineers.
As a result, it now has a feature ‘for users to also provide an indication of impact and severity when filing User Initiated Feedback,’ so that engineers are more likely to be made aware of serious issues.
‘We expect this will allow us to better monitor the impactful issues even when feedback volume is low,’ Cable said.