Windows 11 preview update brings 35 fixes

Microsoft has released the KB5120998 preview cumulative update for Windows 11 versions 25H2 and 24H2, a substantial optional update that delivers 35 changes and fixes. This preview update is not a security update; it focuses exclusively on quality improvements and new functionality.

Testing ground for future patches

KB5120998 is a preview update that lets IT administrators test Windows bug fixes, improvements, and new features before they roll out to all users during next month's Patch Tuesday release. Unlike cumulative updates, monthly optional updates do not include security fixes and provide only quality improvements.

Taskbar flexibility expands

After installing the August 2026 preview update, users can move the taskbar to the bottom, top, left, or right side of their screen in Settings > Personalization > Taskbar > Taskbar behaviors > Taskbar position, with most customization settings, like never combining taskbar icons, working in every position.

The KB5120998 also adds a new smaller taskbar option that reduces the taskbar height and the size of taskbar icons, which is designed to maximize screen space on smaller devices. It also includes small or large size options for the Start menu (in Settings > Personalization > Taskbar > Taskbar behaviors > Taskbar size dialog), as well as the ability to independently show or hide the Pinned, Recommended, and All sections, and to hide the account name and profile picture.

Administrator protection arrives

With KB5120998, Microsoft has also started rolling out the administrator protection security feature that allows users to perform admin tasks using just-in-time privileges.

"Administrator protection is not classified as a formal security boundary; it hardens the security against elevation-of-privilege attacks with the introduction of profile separation," Microsoft said.

— Microsoft, in its announcement

This feature is designed to harden security against elevation-of-privilege attacks by introducing profile separation. The company confirmed that the feature is turned off by default and can be enabled using OMA-URI in Microsoft Intune or through Group Policy.

How to install KB5120998

You can install KB5120998 by opening Windows Settings, clicking on Windows Update, and then clicking 'Check for Updates.' Since this is an optional update, you will need to click the "Download and install" link unless you already have the "Get the latest updates as soon as they're available" option enabled, which prompts the OS to install it automatically. You can also manually download and install the KB5120998 preview update from the Microsoft Update Catalog.

Build numbers and key changes

Once installed, this optional non-security update will upgrade Windows 11 25H2 and 24H2 devices to builds 26200.9278 and 26100.9278, respectively. The August 2026 preview update comes with many other changes, some of the more important ones highlighted below:

• Windows now automatically indexes your most-used folders so those files appear in subsequent search results. You can control the setting at Settings > Privacy & Security > Search > Automatically find additional relevant locations.
• This update improves restart behavior so PCs that were manually put to sleep return to sleep after completing an update, even when automatic sleep is set to Never. This change aims to reduce disruption for users who prefer to keep their systems in sleep mode.
• This update adds support for participating apps to coordinate their updates with Windows Update. Supported apps can benefit from improved scheduling and a more streamlined update experience. For more information, see Windows Update Orchestration Platform (UOP).
• This update improves resiliency and recovery from potential VPN process-related background issues that can cause processes to stop responding. This addresses a common pain point for remote workers who rely on VPN connections.

WMIC deprecation and reboot warning

Starting in August 2026, Windows 11, version 24H2 and 25H2 will no longer include the Windows Management Instrumentation Command-line (WMIC) utility. WMIC is already removed by default in new installations of Windows 11, versions 24H2 and 25H2, and will no longer be available as a Feature on Demand (FoD). This marks a significant shift for administrators who rely on WMIC for scripting and management tasks.

On Thursday, Microsoft warned customers that their systems may reboot one more time after deploying the August 2026 optional update and updates rolling out over the next several months. "With recent and upcoming Windows updates over the next few months, a limited number of consumer and business devices might experience one additional restart during installation," Microsoft noted in a message center update. "This one-time restart occurs after a Secure Boot certificate update is applied as part of the Secure Boot update process."

Support deadlines and upgrade path

Earlier this month, it also reminded customers that devices running Home and Pro editions of Windows 11 24H2 will stop receiving updates in two months. However, Windows 11 24H2 Enterprise and Education editions will remain under mainstream support until October 2027. Users are advised to upgrade to Windows 11 25H2 (also known as the Windows 11 2025 Update), which became generally available in September 2024. This upgrade path ensures continued security and feature updates beyond the 24H2 support cutoff.

Why it matters

This preview update signals Microsoft's ongoing effort to refine Windows 11's user interface and security posture. The taskbar and Start menu customization options address long-standing user requests for greater flexibility, potentially reducing the need for third-party tools. The introduction of administrator protection is a notable security enhancement that could help mitigate elevation-of-privilege attacks, a common vector in cyber incidents. Additionally, the reboot warning and WMIC deprecation are important operational considerations that may require planning, particularly for organizations that rely on WMIC scripts or that have strict reboot policies. As Windows 11 24H2 Home and Pro approach end of support, upgrading to 25H2 becomes increasingly critical to avoid security gaps.