Windows 11 KB5121003 update: 400+ security fixes come with stability trade-off

Microsoft's August 11 mandatory Windows 11 update KB5121003 patched over 400 vulnerabilities but is causing game crashes, system crashes, login errors, and display issues on some PCs. Microsoft has confirmed the problems and opened an investigation. Uninstalling restores stability but strips all 400-plus fixes — a trade-off especially acute for enterprises that may have already pushed the patch fleet-wide.