Windows 11 Update KB5120998 Resets Mouse Settings; September Patch Restores Functionality
What Happened — An optional Windows 11 preview update (KB5120998, August 2026) caused mouse cursor personalization settings to revert to defaults on affected non‑English installations. The reset persisted even after the update was uninstalled. Microsoft released a cumulative update (KB5124008, September 8 2026) that resolves the issue.
Why It Matters for Trust & Control Assurance
- Demonstrates the need for continuous configuration‑change monitoring to detect unintended setting drift after patch deployment.
- Highlights the importance of maintaining auditable evidence that update processes are validated against baseline configurations.
- Aligns with the Control Mapping capability: automated evidence collection proves that configuration controls remain effective post‑update.
Who Is Affected
- Enterprises and end‑users running Windows 11 version 24H2 or 25H2, especially those with non‑English locale settings.
Recommended Actions
- Verify that the September 2026 cumulative update (KB5124008) is installed on all Windows 11 endpoints.
- Run a configuration baseline check on mouse and UI personalization settings to confirm they match the intended state.
- Document the remediation steps in your change‑management system to provide a defensible audit trail.
Technical Notes
- Issue originated from “code components” that failed to load locale‑specific mouse settings, forcing a fallback to default values.
- No CVE was assigned; the problem is a software regression rather than a security vulnerability.
- The bug was limited to the optional preview update but could auto‑install if “Get the latest updates as soon as they’re available” was enabled.
Source: BleepingComputer