Microsoft acknowledged a bug in its August 27, 2026 Windows 11 KB5120998 optional update that causes mouse cursor anomalies and black wallpaper on some systems. The update, which also modifies the taskbar, start menu and Windows Search, was released as part of Microsoft’s regular monthly patch cycle. Users reported that after installing the update the cursor could disappear, become oversized, shrink, or change color, and that wallpaper changes were not persisted, showing a black screen after reboot. Testing by Windows Latest confirmed the issue appeared immediately after installation. Microsoft’s release notes noted that personalization settings may be reverted and that the problem affects updates released on or after August 27, 2026. The company said it is investigating and expects a corrective update in the coming days. Users are advised to uninstall KB5120998 to restore normal functionality. Microsoft has not provided a timeline for a fix, and the issue remains unresolved for affected machines.