At a Glance
- Smart App Control can now be toggled on or off without reinstalling Windows a fix Windows users have waited for since 2023
- Monitors running at 1000 Hz refresh rates, including the Acer Predator XB273U F6 announced at CES 2026, are now officially supported
- File Explorer’s internet-file unblocking works reliably again after the October 2025 security lockdown broke it
- Build numbers are 26200.8116 (25H2) and 26100.8116 (24H2); rollout is currently paused due to install error 0x80073712
Microsoft shipped KB5079391 on March 26, 2026, targeting Windows 11 versions 25H2 and 24H2. Two changes buried inside this optional preview update matter far more than the patch notes suggest. One finally breaks a wall that locked users out of Smart App Control without a full OS reinstall. The other quietly shifts the ceiling on high-refresh-rate display support into territory previously off-limits in Windows.
Smart App Control Toggle: Why This Fix Took Over Two Years
Smart App Control blocks apps Microsoft considers suspicious. Sounds useful. But the design flaw ran deep: once enabled, turning it off required wiping and reinstalling Windows entirely.
Microsoft first announced a fix in January 2026 with KB5074105, then stopped rolling out those changes before they reached most users. KB5079391 is where the toggle actually lands. After installing, go to Settings > Windows Security > App & Browser Control > Smart App Control settings and the toggle works in both directions.
Most reviewers treat this as minor. It isn’t. IT administrators managing fleets of OEM devices where SAC ships pre-enabled have been forced to either accept its behavior or reimage machines, a real operational cost this single toggle eliminates. And SAC is still rolling out gradually, so the toggle won’t appear immediately on every device after install.
1000Hz Refresh Rate Support Changes the Monitor Ceiling
The world’s first 1000Hz gaming monitor, the Acer Predator XB273U F6, was announced at CES 2026. Until KB5079391, Windows had no infrastructure to support displays reporting at that refresh rate through standard APIs.
This update adds that foundation. The 1000Hz feature is also rolling out gradually, so it won’t activate for every user immediately after installing the patch. Existing 240Hz and 360Hz monitors are completely unaffected.
File Explorer Unblocking: What October 2025 Broke, March 2026 Fixes
Windows 11’s October 2025 update blocked preview of internet-downloaded files in File Explorer as a direct defense against NTLM relay attacks. Security teams approved. Everyone who downloads and previews PDFs, images, and documents daily found their workflow disrupted.
Some PowerShell scripts failed to unblock files reliably, and even manually allowing each file through Properties didn’t always work. Microsoft confirmed this as a known issue, and KB5079391 finally makes the unlock process reliable. Zone identifier security tags remain intact; the fix targets the friction, not the underlying security model.
Voice Typing (Win + H) now works when renaming files inside File Explorer too. And the “Advanced Security Settings” popup in File Explorer now lets you sort permissions small, but genuinely useful for power users managing complex ACL setups.
Display and Sleep Reliability: Fixes That Affect Daily Use
Auto-rotation now works correctly after waking from sleep. Devices that rotated orientation during sleep would previously resume in the wrong state until manually corrected. Tablet and convertible laptop users hit this most.
HDR is now more reliable on some monitors. If you’ve seen HDR disengage without explanation, this update likely addresses it. USB4-connected monitors also now allow the USB controller to reach its lowest power state during sleep, which cuts battery draw and power consumption on supported hardware.
Settings App Gets Microsoft 365 Plan-Switching
It’s not a headline feature, but it’s worth flagging. Switching Microsoft 365 plans is now possible directly from Settings > Accounts, without needing a browser. Users on Microsoft 365 Basic can upgrade to Microsoft 365 (which includes Copilot in Office apps) without leaving the OS settings. Dialog boxes under Settings > Accounts > Other users have also been updated to match Windows 11’s current design language.
The Settings app’s home screen has been reorganized: device specifications are easier to find on the About page, and a ‘Device’ card on the Settings home page is rolling out to more users.
Other Confirmed Fixes in KB5079391
Beyond the headline changes, Microsoft patched several stability issues:
- Safe mode was causing taskbar instability fixed
- Voice Access struggled to read and write numbers in English fixed
- Start menu now applies Group Policy layout updates correctly across organization devices
- Windows Hello reliability improved
sfc /scannowwas generating false-positive error messages on healthy systems fixed- ARM64 devices running x64 apps in the Windows Recovery Environment are more stable
Where It Falls Short
Trade-Offs Worth Knowing: KB5079391’s rollout is currently paused by Microsoft due to install error 0x80073712 affecting some devices. Because this is an optional preview update, users who don’t manually opt in won’t receive it at all until Microsoft folds these changes into the April 14, 2026 mandatory Patch Tuesday release. Additionally, both the Smart App Control toggle and 1000Hz refresh rate support are rolling out gradually installing the update doesn’t guarantee these features appear immediately.
Windows 11 Build 26300.7939 Brings Enterprise Security and Audio Sharing You Actually Need
How to Install KB5079391
- Open Settings > Windows Update
- Select Check for updates
- Look under Optional updates available and select KB5079391
- Download and restart when prompted
If you prefer a manual install, Microsoft Update Catalog hosts direct .msu offline installers for both 25H2 (26200.8116, 4,802 MB) and 24H2 (26100.8116, 4,449 MB) builds across x64 and ARM64 architectures. Note: the full Catalog package size is significantly larger than the delta delivered through Windows Update on most devices.
Given the paused rollout status, users on production machines may want to wait for the April 14 Patch Tuesday bundle instead.
