QUICK ANSWER

KB5120998 is the August 27, 2026 cumulative preview update for Windows 11 version 25H2 and 24H2. On Windows 11 25H2 it updates the OS to Build 26200.9278, matching the update shown in your screenshot. Windows 11 24H2 moves to Build 26100.9278. It is a non-security preview update, primarily delivering new Windows features, quality improvements and fixes that Microsoft can later include in regular security updates.

The update is particularly notable because it introduces major customization changes to the Taskbar and Start menu, Windows Search improvements, faster File Explorer Home, Administrator Protection rollout, VPN improvements, post-quantum cryptography support, and other Windows enhancements. It also marks another important change for administrators: the legacy WMIC command-line utility is no longer included in Windows 11 24H2/25H2.

However, Microsoft has already documented known problems with KB5120998, including mouse customization resetting on some non-English Windows installations and desktop backgrounds potentially becoming black or losing customization. There is also an ARM-specific Teams/new Outlook issue associated with August 2026 updates.

Recommendation: Because KB5120998 is a preview/non-security release, business users and administrators who prioritize stability can generally wait for the changes to arrive through a regular Windows security update unless they specifically need one of its fixes or new features.

3) COMPLETE ARTICLE

What is Windows 11 Update KB5120998?

Microsoft released KB5120998 on August 27, 2026 as a cumulative preview update for:

Microsoft describes KB5120998 as containing production-quality improvements, but it is a preview release rather than the normal monthly security update.

The screenshot shown above is an example of Windows Update displaying:

2026-08 Preview Update (KB5120998) (26200.9278)

That indicates a Windows 11 25H2 system being offered the August 2026 preview update.

Microsoft's Update Catalog also lists KB5120998 for both x64 and ARM64 Windows 11 25H2 and 24H2 systems.

Is KB5120998 a Security Update?

No. KB5120998 is a non-security cumulative preview update.

This distinction is important.

Microsoft uses preview releases to deliver quality improvements, fixes and some new functionality ahead of their broader inclusion in subsequent Windows updates.

Therefore, if your computer is working correctly, you generally do not need to rush to install a preview update simply because Windows Update offers it.

For business computers, production systems and PCs running important accounting, ERP, CAD, business or specialized applications, waiting for the regular security update may provide a more conservative deployment strategy.

What's New in Windows 11 KB5120998?

KB5120998 is more substantial than a typical collection of minor bug fixes. It includes several visible Windows interface changes.

1. Taskbar Can Be Moved Again

One of the most interesting additions is expanded Taskbar positioning.

Microsoft says Windows now allows the Taskbar to be positioned at the:

• Bottom
• Top
• Left
• Right

of the screen.

This is particularly significant for users who preferred alternative Taskbar positions in older versions of Windows.

To check the setting, go to:

Settings → Personalization → Taskbar → Taskbar behaviors → Taskbar position

Microsoft notes that features such as tooltips, flyouts and animations adapt to the selected Taskbar location.

However, some options have limitations. For example, the Search box and smaller Taskbar currently support the top and bottom positions.

Important: Gradual Rollout

Do not assume that installation of KB5120998 will immediately make every new feature appear.

Microsoft is using a gradual rollout for a number of these features, which means two PCs with the same Windows version and KB installed can temporarily have different features available.

2. New Smaller Taskbar Option

Windows 11 now introduces a smaller Taskbar option.

This reduces:

• Taskbar height
• Taskbar icon size

while retaining access to Start, Search and the system tray.

Look under:

Settings → Personalization → Taskbar → Taskbar behaviors → Taskbar size

and select Small where the feature is available.

This can be useful on laptops and devices with smaller displays where vertical screen space is valuable.

3. Start Menu Gets More Customization

KB5120998 also introduces several Start menu improvements.

Small and Large Start Menu

Users can select a different Start menu size.

Look under:

Settings → Personalization → Start → Start menu size

Available choices include:

• Automatic
• Small
• Large

Microsoft has also redesigned the Start settings page to provide greater control over individual Start menu sections.

Recommended Becomes Recent

The familiar Recommended section is being renamed Recent.

This change also appears in the corresponding Start settings.

Hide Your Name and Profile Picture

Windows 11 can now hide the user's name and profile picture from Start.

Go to:

Settings → Personalization → Start

and look for:

Hide your name and profile picture on Start

This may be useful on shared screens, presentation PCs or environments where displaying the logged-in user's identity is unnecessary.

4. Windows Search Improvements

Microsoft has made several changes to Windows Search.

The Search Home interface has been simplified, and Windows now makes the origin of a result clearer—for example whether the result is an:

• App
• Setting
• File
• Web result
• Microsoft Store suggestion

Users also gain more control over whether web and Store suggestions appear alongside local search results.

Look under:

Settings → Privacy & security → Search

Another new capability allows Windows to automatically index frequently used folders so their files can appear more effectively in future searches.

The relevant option is:

Settings → Privacy & security → Search → Automatically find additional relevant locations

5. File Explorer Improvements

Microsoft says File Explorer Home should launch faster and respond more quickly after the improvements included with this release.

The Recommended area on File Explorer Home also gains improved touch scrolling.

For users who frequently open File Explorer, especially on laptops and tablets, this is a useful usability improvement.

6. Updated Windows Progress Indicators

Windows progress indicators are being modernized to provide a more consistent appearance during operations including:

• Windows startup
• Sign-in
• Restart
• Shutdown
• Windows Update installation

The change is primarily visual but helps make the Windows interface more consistent.

7. Administrator Protection

KB5120998 begins rolling out Administrator Protection, a security-hardening capability intended to reduce the risks associated with continuously available administrator privileges.

Instead of allowing administrative privileges to remain freely available, Administrator Protection uses just-in-time privileges for administrative operations.

Microsoft states that Administrator Protection is not classified as a formal security boundary, but it is designed to strengthen Windows against elevation-of-privilege attacks through profile separation.

The feature is disabled by default and can be managed in organizational environments through technologies such as Group Policy or Microsoft Intune.

This feature is particularly relevant to IT administrators managing corporate Windows computers.

8. Better Virtual Desktop Switching

Users working with multiple Windows virtual desktops should see smoother and more responsive transitions between desktops.

This is a relatively small change but may benefit power users who frequently organize applications across multiple virtual desktops.

9. Display and Brightness Improvements

KB5120998 improves reliability when opening and using:

Settings → System → Display

It also improves the persistence of brightness settings after Energy Saver is turned off.

10. Task Manager Reliability Improvements

Microsoft has improved the reliability of App History information in Task Manager.

If Task Manager previously failed to display application history information correctly or consistently, this update may improve the experience.

11. Windows Update Restart and Sleep Improvement

There is a useful improvement for laptops and PCs that users manually put to sleep.

After Windows wakes the computer to complete an update, Windows can return the PC to sleep afterward—even when automatic sleep is configured as Never.

This may prevent PCs from remaining unnecessarily awake after Windows Update maintenance.

12. Windows Update Can Coordinate Supported App Updates

Microsoft is expanding Windows Update beyond traditional operating-system servicing.

KB5120998 adds support for participating applications to coordinate their application updates with Windows Update.

Supported applications can benefit from coordinated scheduling and a more unified update experience.

This capability is associated with Microsoft's Windows Update Orchestration Platform.

13. Windows Autopilot Improvements

For enterprise administrators, device association for Windows Autopilot device preparation is now generally available.

The functionality helps organizations identify trusted devices before enrollment and can assist with:

• Device-targeted policies
• Corporate device enrollment
• Customized Out-of-Box Experience (OOBE)
• Automated enterprise provisioning

This is mainly relevant to businesses using modern Windows device-management infrastructure.

14. Microsoft Execution Containers

KB5120998 introduces Process Isolation for Microsoft Execution Containers (MXC).

Microsoft describes this as a lightweight isolation boundary intended for responsive workloads such as coding agents and model-generated code.

Policies can restrict access to resources such as:

• Files
• Networking
• User interface
• Other operating-system capabilities

This represents part of Microsoft's broader work around safely executing agentic and AI-related workloads.

15. Agentic Process Support

Windows is also introducing preview platform support for tagging agentic processes.

Authorized components can assign an opaque agent identifier to a process token. That identifier can be propagated to child processes and included during certain Web Account Manager authentication requests.

Microsoft specifically describes this functionality as a preview capability, meaning its implementation may change.

16. Post-Quantum Cryptography Support

A technically significant addition is expanded support for ML-KEM, a post-quantum cryptographic algorithm.

ML-KEM can now be used as a standalone algorithm for TLS key exchange in addition to previously introduced hybrid approaches.

For typical home users this change will largely operate behind the scenes, but it is significant for the long-term evolution of Windows cryptography.

17. VPN Reliability Improvements

KB5120998 includes improvements designed to make Windows more resilient to certain VPN-related background process problems that could otherwise cause processes to stop responding.

Users experiencing intermittent VPN reliability problems may therefore benefit from this update, depending on the underlying cause.

18. Touchpad and Mouse Improvements

Microsoft has improved touchpad reliability on some devices.

The update targets problems affecting:

• Touchpad gestures
• Mouse dragging
• Pointer interaction

and aims to make these actions respond more reliably.

Ironically, there is also a separate known mouse customization issue discussed later in this article.

19. Important: WMIC Is Being Removed

This is one of the most important changes for system administrators and technicians.

Starting in August 2026, Windows 11 versions 24H2 and 25H2 no longer include the legacy Windows Management Instrumentation Command-line utility (WMIC). Microsoft notes that it was already absent by default from new installations and is no longer available as a Feature on Demand.

Does this mean WMI is removed?

No.

WMIC and WMI are not the same thing.

The legacy command-line utility:

wmic.exe

is being removed.

Windows Management Instrumentation (WMI) itself remains supported.

This distinction is extremely important.

What Should Replace WMIC?

Administrators should migrate old scripts from WMIC to supported PowerShell/CIM commands.

For example, an old command such as:

wmic computersystem get model,name,manufacturer

can generally be replaced with PowerShell:

Get-CimInstance Win32_ComputerSystem |
Select-Object Name, Manufacturer, Model

To obtain BIOS information:

Get-CimInstance Win32_BIOS

For operating-system information:

Get-CimInstance Win32_OperatingSystem

For processor information:

Get-CimInstance Win32_Processor

This change is particularly important for businesses that still use old batch files, inventory utilities, login scripts or support applications dependent on wmic.exe.

AI Component Updates

KB5120998 updates several Windows AI components to version:

1.2608.951.0

Microsoft lists components including:

• Image Search
• Content Extraction
• Semantic Analysis
• Settings Model

However, Microsoft notes that these AI component updates apply to Windows Copilot+ PCs and do not install on ordinary Windows PCs or Windows Server systems where the components are not applicable.

Servicing Stack Update Included

KB5120998 includes servicing improvements associated with KB5120997.

The Servicing Stack Update improves the reliability of the mechanism Windows uses to install updates.

Normally, users do not need to install the servicing stack separately when installing through Windows Update.

Known Problems With KB5120998

This section is especially important if you are deciding whether to install the update.

As of September 7, 2026, Microsoft's KB5120998 documentation lists multiple known issues. Microsoft updated the release documentation on September 2, 3 and 4 as these problems were documented.

Known Issue 1: Mouse Customization Can Reset

On some non-English Windows installations, installing KB5120998 or later updates can cause customized mouse settings to revert to defaults.

Affected settings can include:

• Mouse cursor
• Custom cursor schemes
• Cursor animations
• Other mouse personalization settings

More importantly, simply changing the settings back may not solve the problem because Microsoft says the issue affects how those settings are loaded.

Current Status

Microsoft is working on a resolution that will be delivered through a future Windows update.

Known Issue 2: Desktop Background May Turn Black

Some systems can lose their customized desktop background after installing KB5120998 or later updates.

The desktop may instead display a solid black background.

Other desktop customization settings may also be affected, including:

• Slideshow configuration
• Contrast themes
• Background personalization

Microsoft says manually restoring the settings may not work on affected systems because the problem involves Windows failing to correctly load the saved settings.

Current Status

Microsoft is working on a fix.

This is a good reason for business administrators to test KB5120998 before deploying it widely.

Known Issue 3: Teams and New Outlook on ARM PCs

Microsoft also documents an issue affecting some ARM-based Windows PCs following August 2026 security updates.

Affected applications can include:

• Microsoft Teams
• New Outlook for Windows

They may fail to launch or close unexpectedly.

Devices mentioned by Microsoft include ARM-based systems such as Surface Pro 11 and Surface Laptop 7. Classic Outlook, Word and Excel are not currently known to be affected by this particular problem.

Microsoft recommends updating the Auto Super Resolution Package to version 1.0.19.0 or later through Microsoft Store as a workaround.

Should You Install KB5120998?

The answer depends on how the PC is being used.

Because this is a preview update rather than a security update, there is usually little reason to install it immediately on a stable production computer unless one of its fixes or features is needed.

Should Businesses Install Preview Windows Updates?

For managed business environments, a sensible strategy is:

Test → Pilot → Monitor → Deploy

For example:

Stage 1: Install on an IT/test computer.

Stage 2: Test important business software.

Examples include:

• Accounting software
• ERP software
• VPN clients
• Antivirus/endpoint security
• Printers
• Scanners
• Banking software
• Microsoft Office
• Custom applications
• Database clients
• Remote-access applications

Stage 3: Monitor for several days.

Stage 4: Deploy more broadly only if necessary.

For ordinary production environments, waiting for the fixes to become part of a regular security update is often the lower-risk option.

How to Check Whether KB5120998 Is Installed

Open:

Settings → Windows Update → Update history

Search for:

KB5120998

You can also press:

Win + R

type:

winver

and press Enter.

For Windows 11 25H2, installation of this update should bring the system to:

OS Build 26200.9278

For Windows 11 24H2:

OS Build 26100.9278

Check KB5120998 Using PowerShell

Open PowerShell and run:

Get-HotFix -Id KB5120998

If the update is represented through that interface on the system, Windows will return its details.

You can also review recent installed updates using:

Get-HotFix |
Sort-Object InstalledOn -Descending |
Select-Object -First 20

How to Install KB5120998

The simplest method is Windows Update.

Go to:

Start → Settings → Windows Update

Then check:

Advanced options → Optional updates

Microsoft also makes KB5120998 available through the Microsoft Update Catalog.

Download/Search KB5120998 in Microsoft Update Catalog

For most home and office users, Windows Update is preferable to manually downloading MSU packages.

Important Warning for Manual Deployment

IT administrators manually servicing Windows installation images should pay attention to Microsoft's deployment warning.

When applying applicable Dynamic Updates to installation media, Microsoft says the correct boot.stl file must be included. Failure to do so can prevent systems from starting from that installation media and may result in:

0xc0430001

This warning mainly concerns administrators maintaining or servicing Windows deployment images—not ordinary users installing KB5120998 through Windows Update.

How to Uninstall KB5120998

If you experience serious problems after installation, first check:

Settings → Windows Update → Update history → Uninstall updates

If KB5120998 is offered for removal, select it and follow the instructions.

You can also investigate the installed package state before making changes.

Important

Do not remove Windows updates unnecessarily.

Before uninstalling an update from an important business computer:

1. Back up critical files.
2. Confirm that the problem started after the update.
3. Check Microsoft's latest known-issue information.
4. Restart the PC once before assuming the update is responsible.
5. Consider System Restore or other recovery options where appropriate.

What If KB5120998 Is Stuck Downloading or Installing?

If the update remains stuck, start with simple troubleshooting.

Restart Windows and try:

Settings → Windows Update → Check for updates

If the problem continues, open Terminal or Command Prompt as Administrator and run:

DISM /Online /Cleanup-Image /RestoreHealth

After DISM completes, run:

sfc /scannow

Restart Windows and try Windows Update again.

What do these commands do?

DISM /RestoreHealth checks and repairs corruption in the Windows component store.

SFC /scannow checks protected Windows system files and replaces damaged copies when possible.

These commands are generally preferable to immediately deleting Windows Update folders or manually manipulating servicing files.

Windows 11 24H2 Users Should Also Note End of Support

Microsoft says Windows 11 24H2 Home and Pro reach end of updates on October 13, 2026.

Enterprise and Education editions have a different lifecycle and remain supported until October 12, 2027.

Therefore, Home and Pro users still running 24H2 should plan to move to a supported Windows release rather than relying indefinitely on 24H2.

4) FAQ

What is KB5120998?

KB5120998 is Microsoft's August 27, 2026 cumulative preview update for Windows 11 versions 25H2 and 24H2. It contains new features, reliability improvements and non-security fixes.

What build does KB5120998 install?

Windows 11 25H2 becomes Build 26200.9278, while Windows 11 24H2 becomes Build 26100.9278.

Is KB5120998 a security update?

No. It is a preview/non-security cumulative update.

Is KB5120998 mandatory?

It is a preview update rather than the normal monthly security release. If your PC is stable and you do not need its fixes or early feature rollout, waiting is generally reasonable.

Is KB5120998 safe to install?

Microsoft has released it as a production-quality preview update, but documented known issues exist. In particular, mouse personalization can reset on some non-English Windows installations and some systems may lose desktop-background settings.

Why did my desktop background become black after KB5120998?

Microsoft has confirmed a known issue where some desktop personalization settings fail to load after updates released August 27, 2026 and later, resulting in a solid black desktop background on affected PCs.

Why did my custom mouse cursor disappear?

KB5120998 has a documented issue affecting mouse personalization on some non-English Windows systems. Microsoft is working on a future fix.

Does KB5120998 remove WMIC?

Windows 11 24H2 and 25H2 no longer include the legacy WMIC command-line utility beginning in August 2026. WMI itself remains supported. Administrators should migrate legacy WMIC scripts to modern PowerShell/CIM alternatives.

Should I install KB5120998 on my office computers?

If the computers are stable and the update does not contain a fix you specifically require, it is reasonable to wait. Businesses should ideally test preview updates on a small number of systems before deploying them broadly.

Where can I download KB5120998 manually?

It is available through the official Microsoft Update Catalog.

Microsoft Update Catalog — KB5120998

5) FINAL RECOMMENDATION / CONCLUSION

KB5120998 (Build 26200.9278 for Windows 11 25H2) is an unusually feature-rich preview update, with substantial changes to the Taskbar, Start menu, Search, File Explorer, Administrator Protection and other Windows components. It also brings networking, touchpad, cryptography, Windows Update and enterprise-management improvements.

The WMIC removal is particularly important for IT professionals because older scripts and support utilities may still depend on wmic.exe. Administrators should begin replacing those dependencies with PowerShell and CIM.

At the same time, Microsoft has confirmed known issues affecting mouse personalization and desktop backgrounds, with additional ARM-specific application concerns documented around the August 2026 updates.

For a home PC where you want the newest Windows features, installing the preview can be reasonable after reviewing the known issues.

For a business, accounting, production or mission-critical PC, there is generally no need to rush. Test KB5120998 on a non-critical machine first or wait for the improvements to mature into a regular Windows security update.

Because Microsoft's known-issue information can change after publication, administrators should check the current official KB page before deploying the update widely.

Official Microsoft KB5120998 Release Information

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