Microsoft has acknowledged that the KB5120998 preview update, released in August 2026, inadvertently resets mouse personalization settings on Windows 11 systems, but the company’s investigation reveals that the bug exclusively impacts installations where the operating system language is not English. This known issue, which reverts cursor and cursor animation preferences to a standard default, was confirmed by the company last week, just one day after the optional non-security update became available for devices running Windows 11 versions 25H2 and 24H2. Affected users have reported that mouse cursor settings change or reset automatically without warning, and attempts to restore previous configurations are unsuccessful. The root cause, Microsoft explained in a subsequent update to the Windows release health dashboard, lies in code components used specifically in non-English Windows installations. In affected locales, these components fail to load properly, forcing the system to fall back to default settings instead of applying the user’s customized choices.
Why the KB5120998 bug only affects non-English Windows 11 systems
The KB5120998 update, delivered as part of Microsoft’s August 2026 preview cycle, introduced several improvements to the Start menu, taskbar, and Windows search. However, shortly after its release on August 27, 2026, users began noticing that mouse personalization settings — including the selected cursor style and associated animations — were being overwritten. Microsoft initially confirmed the problem on Friday, August 28, 2026, stating that the issue stemmed from the update itself. A deeper investigation later narrowed the scope: only devices running Windows 11 in a language other than English encounter the reset behavior.
“Our investigation indicates that this issue is caused by code components used in non-English Windows installations. In impacted locales, these settings will fail to load, causing a default to be used instead,” Microsoft noted in the health dashboard. This technical explanation points to a localization-related defect within the update’s code pathways. When the system attempts to retrieve the user’s stored mouse preferences, the relevant components — likely designed to handle regional string resources or locale-specific cursor definitions — do not execute correctly. As a result, Windows defaults to a base set of cursor options, effectively erasing any prior customization.
What causes the mouse settings to reset after KB5120998? The reset is triggered by a failure in the code components responsible for loading personalized mouse settings on non-English Windows 11 installations. When the system cannot load these components, it replaces the user’s cursor and cursor animation preferences with standard defaults. This is not a corruption of the settings file but a runtime loading failure that occurs each time the settings are accessed after the update is applied.
How the update reaches devices and what users can do
KB5120998 is classified as an optional, non-security preview update. By default, users must manually navigate to Windows Update and click the “Download and install” link to apply it. However, Microsoft has enabled a setting — “Get the latest updates as soon as they’re available” — which, when turned on, causes the preview update to install automatically without user intervention. This feature, designed to speed up delivery of non-security improvements, has inadvertently widened the reach of the mouse settings bug. For users who have enabled this option, the update installs silently, and the mouse reset may occur without any prior indication.
For those already affected, Microsoft has not yet released a permanent fix. The company is working on a resolution, likely to be included in a subsequent cumulative update. In the interim, affected users can attempt to manually reconfigure their mouse settings, but the system may revert them again after a restart or further updates. Rolling back the KB5120998 update through the Windows Update recovery options is a viable workaround, but this requires administrative privileges and may not be straightforward for all users. Microsoft advises that users who have not yet installed the update and wish to avoid the issue should temporarily disable the “Get the latest updates” toggle and refrain from the manual download.
Broader context: A history of mouse-related bugs in Windows
This is not the first time Microsoft has had to address mouse functionality issues on Windows devices. In recent months, the company has dealt with several other bugs that affected pointing devices, highlighting a recurring area of instability in the operating system’s input handling. In October 2025, Microsoft released an emergency update to fix a known issue that made the Windows Recovery Environment (WinRE) unusable. The problem arose because certain updates disabled USB mice and keyboards when booting into recovery mode, leaving users unable to navigate diagnostic tools.
More recently, Microsoft confirmed that it is investigating a bug in the classic version of Outlook that causes the mouse pointer to disappear entirely when moved over the interface. This issue, while separate from the KB5120998 reset problem, underscores the complexity of maintaining consistent input device behavior across different Windows components and applications.
Additionally, Microsoft acknowledged on Wednesday that the same KB5120998 preview update can also cause desktop settings — such as icon layout and wallpaper — to be lost or reset on some devices. This suggests that the underlying code flaw may have broader implications beyond mouse customization, potentially affecting multiple user preference stores that rely on the same localized components.
What this means for enterprise and non-English-speaking users
The localization-specific nature of this bug carries significant implications for enterprise environments and users in non-English-speaking regions. Organizations that deploy Windows 11 in languages such as French, German, Japanese, or Spanish may find that their standardized mouse configurations — often set through Group Policy or MDM profiles — are overridden after the update. Even if IT administrators push settings via policy, the runtime failure may still cause defaults to appear at the user level, creating a mismatch between intended and actual behavior.
For individual users, the frustration lies in the loss of accessibility or personalization settings. Many users rely on high-contrast cursors, large pointers, or custom animations to accommodate visual impairments or simply to improve productivity. The automatic reset to standard settings forces them to reapply these preferences repeatedly, which can be both time-consuming and disorienting.
Microsoft has not indicated whether the bug will be patched in the upcoming Patch Tuesday release or via a separate out-of-band update. Given that KB5120998 is a preview update, the company may choose to incorporate the fix into the final September 2026 cumulative update. However, the delay could leave affected users exposed for several weeks.
Technical analysis: Understanding the code component failure
While Microsoft has not published detailed source-level information, the description of “code components used in non-English Windows installations” points to a common class of software defect known as a localization regression. In such cases, the update may have altered or replaced certain resource files — such as .mui (Multilingual User Interface) files or cursor definition tables — that are specific to each language. When Windows tries to read the user’s saved pointer scheme, it looks for a resource that is expected in a particular locale. If the update modified the structure of those resources without updating the corresponding retrieval code, the system cannot locate the correct data and defaults.
Another possibility is that the update introduced a new dependency on an English-only component, causing a silent failure on non-English systems. For example, a function that previously accepted a locale identifier might now assume a default English value, breaking the retrieval chain for other languages. Such issues are notoriously difficult to catch during testing if the quality assurance process focuses primarily on English configurations.
This incident also highlights a broader challenge in maintaining global software: even minor changes to shared code can have cascading effects on localized features. Microsoft’s rapid identification of the locale-specific nature of the bug suggests that the company has improved its telemetry and diagnostics for language-related failures, but the impact nonetheless demonstrates the need for more rigorous regression testing across all supported languages.
Practical consequences for Windows 11 users today
For the immediate term, non-English Windows 11 users who have already installed KB5120998 face a choice: either live with the reset mouse settings until a fix arrives, or uninstall the update to restore previous behavior. Uninstalling a preview update is relatively straightforward: users can navigate to Settings → Windows Update → Update history → Uninstall updates, select KB5120998, and restart. However, this also removes the Start menu, taskbar, and search improvements included in the update, which may be undesirable.
Users who have not yet installed the update should consider delaying it unless they specifically need the new features. Toggling off the “Get the latest updates” option will prevent automatic installation. Enterprise administrators can also block the preview update using Windows Update for Business policies or by setting deadlines that exclude preview releases.
The mouse settings reset problem is not a security vulnerability, but it does affect usability and consistency. For many users, the cursor is an essential navigation tool, and unexpected changes can disrupt workflows and cause confusion, especially in shared or managed environments.
Looking forward: Implications for Microsoft’s update strategy
This incident raises questions about the reliability of optional preview updates as a vehicle for delivering feature improvements. While such updates allow Microsoft to gather feedback before a broader rollout, they also introduce risk to users who opt in — especially those who may not be aware that the update can alter system settings. The fact that the bug only manifests on non-English systems also suggests that Microsoft’s testing coverage may not be evenly distributed across language packs. The company may need to invest in more localized test matrices to catch such issues before release.
Furthermore, the simultaneous reports of desktop settings being reset after the same update indicate that the problem may be more systemic than initially thought. If multiple preference categories are affected, the root cause could be a central settings service that fails to load correctly on non-English systems. Microsoft’s investigation is ongoing, and users should expect a more detailed technical explanation once a fix is issued.
As Windows 11 continues to receive regular feature updates under the “moments” model, incidents like this serve as a reminder that operating system-level changes, even those aimed at improving user experience, can inadvertently degrade it. The balance between innovation and stability remains delicate, and for non-English-speaking users, this latest bug underscores that localization is not merely a translation exercise — it is a deep engineering concern that touches every part of the codebase.
