Overview
- The optional KB5120998 preview, which shipped on August 27, 2026, brought UI changes such as a movable taskbar and resizable Start menu and was followed by widespread reports of mouse cursor regressions and wallpapers turning black.
- Microsoft updated its release notes to confirm it has received reports that cursor personalization settings are being changed or reverted after installing updates released August 27 (KB5120998) and later and says it is investigating.
- Affected users report the cursor can disappear, become very large or small, or revert to default colors and animations, and community testing shows the problems appear immediately after install and go away after uninstalling KB5120998.
- Reporters and users recommend uninstalling the optional preview as the practical mitigation by going to Settings > Windows Update > Update history > Uninstall, locating KB5120998, and removing it, and Microsoft asks affected users to file Feedback Hub reports.
- Because KB5120998 is an optional preview offered to production PCs rather than a security Patch Tuesday release, many non‑Insider systems saw the change and the incident has renewed questions about Windows update testing and quality controls.