Microsoft has released cumulative update KB5121132 (Build 28120.2760) for Windows 11 version 26H1, intended for insiders on the Experimental channel. This update brings several notable improvements to File Explorer, Microsoft Store, and the input system, and also contains a fix for an issue with the mouse pointer not displaying in some applications.
- File Explorer. PDF files and other files, except HTML, downloaded from the internet now automatically appear in the preview pane.
- Microsoft Store. Added support for in-app purchases in packaged WinUI 3 applications that require elevation. Developers will be able to offer purchases through Microsoft's built-in commerce platform.
- Input. Fixed an issue introduced in recent builds where the mouse pointer did not appear in some applications.
- App compatibility. Due to a known compatibility issue with PUBG: BATTLEGROUNDS, the game may fail to launch after installing this build. The restriction is intentional to avoid stability issues while Microsoft works on a fix together with the game developer. The company promises to share details and a timeline later.
The update is installed through Windows Update: go to Settings > Windows Update and click Check for updates. A computer restart is required to complete the installation. This update is distributed only to Windows Insider Program participants on the Experimental channel and is not intended for regular users of the stable version of Windows 11.
| Feature / Change | Performance Increase or Decrease | Optimization | PC Speed Impact | Gaming Optimization |
|---|---|---|---|---|
| File Explorer preview pane now shows PDF and other non-HTML downloaded files | 🟡 Slight decrease possible (more background rendering) | 🟢 Improved file inspection without opening apps | ⚪ No measurable change | ⚪ Not applicable |
| Microsoft Store supports in-app purchases in elevated packaged WinUI 3 apps | ⚪ No direct impact | 🟢 Better for developers and commerce | ⚪ No change | ⚪ Not applicable |
| Fix: mouse pointer not appearing in some applications | 🟢 Slight increase (less UI lag or redraw issues) | 🟢 Improves usability and responsiveness | 🟢 Minor improvement in affected apps | 🟢 Minor improvement (better input feedback) |
| PUBG: BATTLEGROUNDS launch block due to known compatibility issue | 🔴 Temporary decrease for affected users | 🔴 Intentional restriction to avoid crashes | ⚪ No general PC speed change | 🔴 High negative impact (game may fail to launch) |
Find and Change Settings
| Setting | Where to find | How to change |
|---|---|---|
| File Explorer Preview Pane | File Explorer > View > Preview pane | PDF files and other files, except HTML, downloaded from the internet now automatically appear in the preview pane. To show or hide the preview pane, open File Explorer, click the View menu, and select Preview pane. To change which file types show previews, you may need to adjust associated preview handlers in the system or disable the preview pane entirely. |
| Microsoft Store In-App Purchases | Microsoft Store > App settings > Developer options | Added support for in-app purchases in packaged WinUI 3 applications that require elevation. Developers can offer purchases through Microsoft's built-in commerce platform. To enable or test this functionality, open Microsoft Store, go to app settings, and ensure developer options are enabled. No end-user action is required for purchase support in supported apps. |
| Mouse Pointer Visibility | Settings > Bluetooth & devices > Mouse | Fixed an issue where the mouse pointer did not appear in some applications. No manual change is required after installing the update. If you still experience missing pointer issues, open Settings > Bluetooth & devices > Mouse and adjust pointer size, color, or enable pointer trails to improve visibility. |
Official announcement on the Microsoft website.
The last 10 Windows updates:
| Update | Build | Version | Windows | Channel | Date |
|---|---|---|---|---|---|
| KB5121132 | 28120.2760 | 26H1 | Windows 11 | Experimental | 2026-08-21 |
| KB5124040 | 26220.9223 | 25H2 | Windows 11 | Beta | 2026-08-21 |
| KB5124042 | 26340.9233 | 26H2 | Windows 11 | Experimental | 2026-08-21 |
| KB5121106 | 28020.2731 | 26H1 | Windows 11 | Beta | 2026-08-17 |
| KB5121109 | 28120.2738 | 26H1 | Windows 11 | Experimental | 2026-08-17 |
| KB5124036 | 26220.9202 | 25H2 | Windows 11 | Beta | 2026-08-17 |
| KB5124038 | 26340.9212 | 26H2 | Windows 11 | Experimental | 2026-08-17 |
| KB5120996 | 28000.2796 | 26H1 | Windows 11 | Preview | 2026-08-14 |
| KB5120998 | 26200.9267 | 25H2 | Windows 11 | Preview | 2026-08-14 |
| KB5120240 | 22631.7517 | 23H2 | Windows 11 | Stable | 2026-08-11 |