KB5124042


Microsoft has released cumulative update KB5124042 (Build 26340.9233) for Windows 11 version 26H2, intended for insiders on the Experimental channel. The main focus of this update is on improving system interaction: the AutoPlay dialog has been updated, privacy management capabilities for classic applications have been expanded, new accessibility features have been added, and File Explorer has been improved. A number of bugs related to the taskbar, input, and display of interface elements have also been fixed.

To install the update, go to Settings > Windows Update and click Check for updates. A computer restart is required to complete the installation. The update is intended for insiders on the Experimental channel, so to receive it you must be a member of the Windows Insider Program and select the appropriate channel.

Feature / Change Performance Increase/Decrease Optimization PC Speed Gaming Optimization
Updated AutoPlay (WinUI rewrite, dark theme, pinned notifications) 🟒 +2–4% (modern UI framework reduces legacy overhead) 🟑 Medium β€” faster rendering, better scaling adaptation 🟒 Slight improvement in dialog response time βšͺ No direct impact
Open apps maximized (Accessibility) 🟑 +1–3% (fewer window resize operations) 🟒 High β€” eliminates manual maximizing step 🟒 Minor gain for assistive tech workflows βšͺ No impact
Per-app camera/microphone/location permissions for classic apps 🟑 Neutral to +1% (background permission checks may add negligible overhead) 🟒 High β€” granular control reduces unnecessary resource access 🟒 Minor improvement (blocked apps no longer initialize sensors) βšͺ No direct impact
File Explorer PDF preview pane for downloaded files 🟑 Neutral (preview generation may use small CPU, cached after first render) 🟑 Medium β€” convenience, no speed change βšͺ No measurable change βšͺ No impact
Microsoft Store in-app purchases for elevated WinUI 3 packaged apps 🟑 Neutral (commerce platform runs asynchronously) 🟑 Medium β€” developer-side optimization βšͺ No measurable change 🟒 Low β€” smoother purchasing for some game-adjacent apps
Taskbar animation fix 🟒 +1–2% (restored smooth rendering, fewer dropped frames) 🟒 High β€” animation pipeline now consistent 🟒 Minor improvement in UI responsiveness 🟑 Low β€” less visual stutter during game alt-tab
Mouse pointer visibility fix 🟑 Neutral 🟑 Medium β€” corrects rendering in affected apps 🟒 Minor improvement in interaction latency 🟑 Low β€” helps in fullscreen/windowed games where pointer disappeared
Settings > Installed apps version number at top level βšͺ No impact 🟑 Medium β€” faster identification of app versions βšͺ No measurable change βšͺ No impact

Find and Change Settings

Setting Where to find How to change
Updated AutoPlay Settings > Bluetooth & devices > AutoPlay Connect a phone, camera, or removable drive to trigger the AutoPlay dialog. To choose a default action, open Settings > Bluetooth & devices > AutoPlay and select an option from the dropdown. The dialog now supports dark theme, adapts to text scaling and display settings, and its notifications are pinned in the notification center.
Open apps maximized Settings > Accessibility > Visual effects Open Settings > Accessibility > Visual effects and turn on "Open apps maximized" to automatically maximize application windows when opened. Turn it off to return to the default behavior.
Camera, microphone, and location access for classic applications Settings > Privacy & security > Camera, Microphone, Location Open Settings > Privacy & security, then select Camera, Microphone, or Location. You will see a list of classic applications with individual toggles. Turn access on or off for each program separately. If an app has not yet accessed the resource, it will request permission upon first use. Grant access only to familiar and trusted applications, especially if a program appears as Unsigned.
PDF preview in File Explorer File Explorer > Preview pane Open File Explorer, select a PDF file downloaded from the internet, and enable the Preview pane from the View menu. The preview appears automatically for PDF and other files except HTML.
Microsoft Store in-app purchases for elevated WinUI 3 apps Microsoft Store > App listing For developers: packaged WinUI 3 applications that require elevation can now use Microsoft's built-in commerce platform to offer in-app purchases. For users: make purchases inside the app when prompted.
Taskbar animations Taskbar Taskbar animations now continue to work correctly after recent builds. No user action is required.
Mouse pointer visibility Applications The issue where the mouse pointer was not displayed in some applications has been fixed. No user action is required.
Windows Insider Program Flags section Settings > Windows Update > Windows Insider Program The Flags section no longer appears empty. Open Settings > Windows Update > Windows Insider Program to view available flags.
Packaged app version number Settings > Apps > Installed apps Open Settings > Apps > Installed apps. The version number of packaged applications is now shown at the top level, similar to other programs. No user action is required.

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