Microsoft Confirms KB5120998 Bug Targets Non-English Windows 11 Systems

"Following installation of Windows updates released August 27 2026 (KB5120998) and later, mouse personalization settings are being reverted to certain standard settings," Microsoft explained.

Microsoft pins the problem to code used in non‑English installations

In an update to the Windows release health dashboard, Microsoft said a follow‑up investigation shows the mouse personalization bug introduced by the KB5120998 August 2026 preview update affects only non‑English Windows 11 systems. "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," the company wrote.

Microsoft confirmed the issue the day after releasing KB5120998, which is a preview update that includes Start menu, taskbar, and Windows search improvements for devices running Windows 11 versions 25H2 and 24H2.

What users are seeing: personalization settings revert and cannot be restored

User reports collected after the update said mouse cursor personalization settings are changing or resetting automatically once KB5120998 is installed. Affected users report they cannot restore their previous mouse settings after those settings are reverted; the changes include cursor selection and cursor animations configured under Mouse Properties. Microsoft acknowledged those specific behaviors in its advisory.

How the update is delivered and who may get it unintentionally

KB5120998 is an optional, non‑security preview update, so users must click the "Download and install" link to apply it. Microsoft cautioned, however, that if the "Get the latest updates as soon as they're available" option is enabled, the preview update will install automatically — meaning some devices can receive the change without an explicit manual download.

The combination of optional preview status and an automatic‑install setting has implications for machines configured to accept early updates, particularly those running non‑English installations that the company now says are at risk.

Context: other recent mouse and desktop setting problems

Microsoft has addressed multiple mouse‑related issues in recent months, the company noted. In October, it released emergency updates to fix a known issue that made the Windows Recovery Environment (WinRE) unusable by disabling USB mice and keyboards. More recently, Microsoft confirmed it is investigating a bug that causes the mouse pointer to disappear for some classic Outlook users when moving it over the interface. On Wednesday, Microsoft also acknowledged that Windows desktop settings will be lost or reset on some devices after installing the KB5120998 preview update.

What this means for end users, enterprise IT teams, and help desks

• End users on non‑English Windows 11 installs: Expect cursor and animation settings selected in Mouse Properties to potentially revert to defaults after installing KB5120998. If you prefer your existing personalization, do not click "Download and install" for this optional preview update unless you accept the risk or need the Start/taskbar/search improvements it contains.
• Enterprise IT and update managers: KB5120998 targets Windows 11 25H2 and 24H2 and is optional. IT teams should consider their configuration for the "Get the latest updates as soon as they're available" option and whether preview updates are allowed in production images, particularly for devices using non‑English locales. Escalation paths to Microsoft may be needed for users who report lost desktop or mouse settings.
• Help desks and support staff: Prepare to assist users whose cursor and cursor animations are reset and who report being unable to restore prior settings; note Microsoft’s diagnostic that the issue stems from code components in non‑English installations rather than from user actions.

Microsoft has narrowed the scope of the problem to non‑English installations and described the mechanism causing the defaults to load. For now, the practical choice for affected users and administrators is whether to accept the optional preview update or delay installation until Microsoft issues a corrective update or further guidance via the Windows release health dashboard.

Source: BleepingComputer — Microsoft: KB5120998 mouse reset bug affects only non‑English PCs