Windows 11 KB5120998 Resets Your Mouse Cursor and Turns Wallpaper Black: How to Fix It

Your mouse cursor went back to the default white arrow, your custom pointer scheme disappeared, or your wallpaper turned solid black after a restart. If you installed a Windows 11 update in the last few days, KB5120998 is the cause. Microsoft confirmed the bug on August 29, 2026. Uninstalling the update fixes it for most people.

What Is KB5120998 and Why Did It Break My Cursor?

KB5120998 is an optional preview cumulative update for Windows 11 versions 24H2 and 25H2, released August 27, 2026. It bundles shell customization changes, Autopilot device preparation, and Administrator protection rollout features, and one of those changes resets personalization settings on install.

After installing it, users report:

• Custom cursor schemes reverting to the Windows default arrow
• Cursor size and color settings resetting even after being changed again
• High-DPI custom cursors replaced with oversized plain white cursors
• Desktop wallpaper turning solid black after changing it and restarting
• Blurry or broken text rendering on some displays, though this is less common

Microsoft posted on its release health dashboard: it is investigating the cursor and wallpaper reports. As of this writing, no patch has shipped. The only working fix is removing KB5120998 from your system.

How Do I Check If KB5120998 Is Installed?

Open Settings, go to Windows Update, then Update history, and look for KB5120998 in the list dated August 27, 2026 or later.

Here's the exact path:

1. Press Windows key + I to open Settings.
2. Click Windows Update in the left sidebar.
3. Click Update history.
4. Scroll to the list under Other updates and look for "2026-08 Cumulative Update Preview for Windows 11" with the number KB5120998.

If you see it there, this is your bug. If you don't see it but still have the symptoms, check for a more recent preview build, since Microsoft occasionally reissues these packages under a new KB number with the same underlying code.

How Do I Uninstall KB5120998?

Go to Settings > Windows Update > Update history > Uninstall updates, find KB5120998 in the list, and click Uninstall. Your PC will restart to complete the removal.

Step by step:

1. Open Settings (Windows key + I).
2. Go to Windows Update.
3. Click Update history.
4. Scroll down and click Uninstall updates near the top of the page.
5. Find KB5120998 in the list.
6. Click Uninstall next to it, then confirm.
7. Restart your PC when prompted.

Since KB5120998 is an optional preview package, removing it does not touch your mandatory August 2026 security updates. Those install through a separate KB number and stay in place.

Why Didn't Uninstalling Fix My Cursor Right Away?

Windows caches personalization settings separately from the update itself, so the cursor sometimes stays broken until you manually reapply your settings after the restart.

Go to Settings > Personalization > Mouse pointer and touch, or search "Change pointer size and color" in the Start menu, and set your cursor scheme again. If you were using a third-party cursor pack, reinstall it or reapply it through its own settings app.

For a full reset if the pointer still looks wrong:

1. Search "mouse settings" in the Start menu and open it.
2. Click Additional mouse settings, which opens the older Mouse Properties window.
3. Go to the Pointers tab.
4. Select your preferred scheme from the dropdown, or click Use Default to force a clean reset, then reapply your custom scheme.
5. Click Apply, then OK.

Why Is My Wallpaper Still Black After Uninstalling?

The black wallpaper bug sometimes leaves a corrupted cache entry pointing to a null image, so Windows keeps loading black instead of your picture even after the update is gone.

Fix it by resetting the wallpaper source directly:

1. Right-click the desktop and choose Personalize, or go to Settings > Personalization > Background.
2. Under Personalize your background, change the dropdown to Solid color, pick any color, and apply it.
3. Switch the dropdown back to Picture and choose a wallpaper again, ideally a different image file from the one active when the bug hit.
4. Restart your PC to confirm the setting held.

If the wallpaper still reverts to black after a restart, delete the cached transcoded wallpaper files. Open File Explorer, paste this path into the address bar, and delete everything inside:

%APPDATA%\Microsoft\Windows\Themes\TranscodedWallpaper

Windows regenerates this file automatically the next time you set a wallpaper.

How Do I Stop KB5120998 From Reinstalling?

Pause optional updates through Windows Update settings so KB5120998 doesn't come back on its own the next time Windows checks.

1. Open Settings > Windows Update.
2. Click Advanced options.
3. Turn off Get the latest updates as soon as they're available, which controls optional preview rollouts.
4. Or use Pause updates and set it for up to 5 weeks to block all updates temporarily, not only previews.

Optional preview updates like this one only install if you manually click "Download and install" under Windows Update, or if the toggle in Advanced options is on. If you didn't click anything and still got it, the toggle was likely already enabled from a previous session.

When Will Microsoft Fix This Officially?

Microsoft typically folds preview update fixes into the next mandatory Patch Tuesday release, which falls on September 8, 2026 this month.

Preview updates act as a testing ground for features headed into the next full monthly rollup. Given the pattern from past incidents, such as the KB5121003 game-crashing bug from August 2026, expect Microsoft to ship a corrected version of these shell customization changes with the September cumulative update rather than patch KB5120998 itself. Keep automatic updates paused for previews until you see confirmation the fix landed, then check Windows Update again for the September rollup.

Bottom Line

KB5120998 broke cursor personalization and wallpaper settings for a meaningful number of Windows 11 users starting August 27, 2026. Uninstall it through Settings > Windows Update > Update history > Uninstall updates, reapply your cursor and wallpaper settings manually if they don't snap back on their own, and pause optional preview updates until Microsoft ships a real fix in the September Patch Tuesday release.