Microsoft has confirmed that a recent update for Windows is causing some PCs to freeze or hang after applying the patch. However, the problem might be more widespread than Microsoft is admitting at the moment.
The security update in question includes improvements and fixes that were part of update KB4489892 released last month, Microsoft says. It was primarily meant to provide further mitigations against Spectre and Meltdown, but included other fixes as well.
Since rolling out, some users of certain third-party antivirus software have been complaining of lockups. Microsoft acknowledged the issue in a recent support article, and has temporarily blocked the update to devices running some versions of Sophos Endpoint.
Unfortunately, Sophos users are not the only ones affected.
"Avast customers are reporting their Windows machines with Avast for Business and Avast CloudCare products are becoming stuck or frozen on the login/Welcome screen ... Avast is currently researching the causes and potential solutions to this issue in order to resolve it for our customers," Avast said.
Avast is working on a fix of its own, but in the meantime, it says users can sidestep the issue by booting into Safe Mode and then uninstalling updates KB4462223, KB4493472, KB4493448, KB4464520, KB4462230 and KB4493435.
Some users have also reported similar symptoms on machines running both free and paid versions of Avira's antivirus products. Avira said it has been able to reproduce the error, and that it "is occurring because of a current Windows update."
Likewise, Avira recommends rolling back the recent updates, and specifically KB4493509 on Windows 10 PCs, and KB4493472 and KB4493448 on Windows 7s systems, while it also works on a fix.
Unwanted side effects are unfortunately the nature of the beast when it comes to applying Windows updates. The good news is, Windows 10 is about to become less pushy about updates with the upcoming May 2019 update. While not a perfect solution, all Windows users (including Home) will be able to delay updates for up to 35 days, albeit in 7-day increments.
Bugs may still slip through, but at least this way users will have the option of delaying patches to ensure that there are no annoying issues before committing to installing them.