Microsoft has confirmed a critical bug in its latest cumulative update, affecting millions of Windows 10 and Windows 11 users. The issue leads to a "Restart and Shut Down" loop, preventing users from completing the update and locking them out of their devices. This disruption is particularly severe for corporate IT departments, with reports of entire office networks being paralyzed. The problematic update, identified as KB5037853, was meant to address security vulnerabilities but has caused systems to display an endless "Update and Restart" message. Some users experience a "Blue Screen of Death" (BSOD) and may be forced into "Recovery Mode." Microsoft is working on a "Known Issue Rollback" (KIR) to automatically undo the problematic code for consumer machines, while enterprise users may require manual intervention. The downtime is projected to result in significant financial losses, with large enterprises potentially losing up to ,600 per minute of unplanned downtime. Affected versions include Windows 11 22H2, 23H2, and Windows 10 22H2. Symptoms include failure to shut down, BSOD on boot, and missing Start menu icons. The estimated downtime ranges from 4 to 12 hours, depending on IT response speed. Critics have raised concerns about Microsoft's development process, suggesting it places users in the role of beta testers.