KB5120998 leaves the Windows 11 desktop solid black, still unacknowledged (August 29, 2026)
Chapters
What people are seeing
The desktop goes black. Not a black wallpaper image: a solid black colour where the background used to be. Setting the wallpaper again appears to work, and then the desktop is black again after the next restart.
It arrives with the same update as the cursor problem covered in the August 28 post: KB5120998, on OS builds 26200.9278 for Windows 11 25H2 and 26100.9278 for 24H2. Windows Latest lists the cursor symptoms alongside it, including animations breaking, cursors appearing significantly larger, colour shifts and custom schemes reverting.
TL;DR
Windows 11 desktops are turning solid black after the optional update KB5120998, and as of August 29, 2026 Microsoft has acknowledged only the mouse cursor half of the same failure, according to Windows Latest that day. Microsoft's release notes say it "has received reports indicating that mouse cursor personalization settings are being changed or reverted to certain standard settings" and that it is investigating whether the update caused the problem. The wallpaper reset has multiple confirmed complaints and no matching entry, and setting the wallpaper again does not survive a restart.
- The symptom: the desktop background becomes a solid black colour and returns to black on restart even after the wallpaper is set again.
- Microsoft's acknowledgement covers the cursor only, and it says it is investigating whether the update is the cause.
- As of August 29, 2026 the wallpaper reset has no formal acknowledgement despite multiple confirmed complaints.
- KB5120998 is a preview update released on August 27, 2026 for OS builds 26200.9278 and 26100.9278, so removing it costs features rather than security patches.
- Uninstalling KB5120998 is the only published remedy, and re-setting the wallpaper is not a workaround because it does not hold.
What Microsoft has acknowledged, and what it has not
Microsoft's position on August 29, 2026 covers one symptom of two. Its release notes say Microsoft "has received reports indicating that mouse cursor personalization settings are being changed or reverted to certain standard settings", and that it is investigating whether the update caused the problem. That is an acknowledgement, not a cause and not a fix.
The wallpaper is absent from it. Windows Latest reports multiple confirmed complaints about backgrounds resetting to a black screen on restart, with no formal Microsoft entry to match. That gap is the story of the day: one update, two personalization failures, and only one of them on the record.
What KB5120998 actually is
KB5120998 is the August 27, 2026 preview update for Windows 11 25H2 and 24H2, OS builds 26200.9278 and 26100.9278 (Microsoft Support, August 27, 2026). Being a preview, it is offered rather than required.
What it carries is a set of interface changes: a repositionable taskbar, a smaller taskbar size option, selectable Start menu sizing, and administrator protection off by default. Those are the features you lose by removing it, and they are the whole of what you lose.
| Item | Detail |
|---|---|
| Update | KB5120998, preview, released August 27, 2026 |
| Builds | 26200.9278 (25H2) and 26100.9278 (24H2) |
| Acknowledged symptom | mouse cursor personalization reverting |
| Unacknowledged symptom | desktop background resetting to solid black |
| Microsoft status on August 29, 2026 | investigating whether the update caused the cursor problem |
| Fix | none |
| Remedy | uninstall KB5120998 |
Why removal is cheap this time
Removal is unusually cheap here, and Windows Latest makes the point directly: removal is free because KB5120998 is an optional update, so taking it off does not leave the machine missing security content. That is not true of a Patch Tuesday update, and it is why removal is a reasonable first move rather than a last resort.
The thing that does not work is manually re-setting the wallpaper. It holds until the next restart and then the desktop is black again, which is a good way to lose an hour to a setting that was never going to stick.
What you can do today
As of August 29, 2026, in order:
1. Confirm the update is on the machine. Settings > Windows Update > Update history, look for KB5120998. Or press Windows and R, type winver, and check for build 26200.9278 or 26100.9278.
2. Set the wallpaper once and restart. If the desktop comes back black, you are looking at this fault rather than a theme or a background setting somebody changed.
3. Uninstall KB5120998: Settings > Windows Update > Update history > Uninstall, select it, then restart.
4. Stop re-setting the wallpaper in the meantime. It does not survive a restart while the update is installed.
5. Accept the feature loss knowingly: the repositionable taskbar, the smaller taskbar option, Start menu sizing and administrator protection off by default came with this update and go back with it.
6. If you have not installed KB5120998 yet, leave it alone this week. It is a preview update, and as of August 29, 2026 one of its two personalization faults has not even been acknowledged.
If you would rather hand the removal and the check to someone else, Get XLAnt.
Frequently asked questions
Is it safe to remove KB5120998?
It is a preview update rather than a security update, so removing it does not leave the machine missing patches. What it does cost is the features it carried: the repositionable taskbar, the smaller taskbar size option, Start menu sizing and administrator protection off by default.
Has Microsoft confirmed the black desktop?
Not as of August 29, 2026. Its release notes acknowledge reports about mouse cursor personalization and say it is investigating whether the update caused that. The wallpaper resetting to a black screen on restart had multiple confirmed complaints and no formal entry.