A new security update meant to provide protection against the security vulnerabilities Spectre and Meltdown for Windows 7, 8.1, and 10 is causing systems to freeze up and hang on startup.
According to the Windows 7 and 8.1 update history pages, the new update causes systems using certain antivirus software to stop responding shortly after startup. The page lists Avira, Avast, Sophos, and ArcaBit to be the antivirus softwares that are known to have the issue with the new update.
For Windows 10 systems on the other hand, the update history page only lists ArcaBit as an antivirus software that is having issues with the new update.
Microsoft added that they are temporarily blocking the update on Windows 7 and 8.1 systems that have Avira and Sophos installed until a proper solution is available.
It is recommended that users facing the issue boot their system into safe mode and uninstall the update. The updates causing the issue are KB4493472 and KB4493448 on Windows 7, KB4493467 and KB4493446 on Windows 8.1, and KB4493509 on Windows 10.
Microsoft had previously added an automatic rollback feature last month to deal with updates that prevented startup of a device. However as the current update only displays issues after startup, it was not automatically removed.