Windows Defender Not Working in Latest Windows 11 Preview Build: Here’s How To Fix It

Build 20000.120 comes with a critical security bug.

The latest Windows 11 preview build comes with a critical security bug that affects Windows Defender. Build 20000.120, the latest build to be released in both the Dev and Beta channels, has an issue with Windows Defender when you try to open it. When you go to the Windows Security tab inside settings and click on the “Open Windows Security” button, it shows a strange pop-up instead of opening the application.

The pop-up reads “You’ll need a new app to open this windowsdefender link“, beneath which it gives you to option to search the Microsoft Store for an app. This dialog box is similar to what comes up when you try to open or access a file whose extension is either unsupported by the default app set in the respective category (e.g. .MPG in the Photos app), there is no app set as default for said extension, or the extension is entirely invalid itself.

Source: Techdows

So, it’s obviously worrying that a core element of Windows is giving the same error as a third-party file might, an element as crucial as security. Fortunately though, this issue is not prevalent on a large-scale as only a few users are reportedly facing this error. However, that number is still large enough that this has become a glaring issue that Microsoft will likely patch in the next update.

Windows 11’s Security and Windows Defender’s Problems

Microsoft has gone all in on security in Windows 11 with astonishingly high hardware requirements that block off basically all processors released before 2017. Your motherboard or CPU also needs to have TPM 2.0 built-in along with Secure Boot. That kind of spec limits the devices able to officially run Windows 11 significantly, but Microsoft says this will allow for more fortified security and protection against malware, viruses, ransomware, and other security threats.

Expectedly, an outrage from the community followed mocking Microsoft’s unreasonable requirements but Microsoft re-iterated the logic behind their decision, shutting down any hopes for a revision of the hardware requirements. Hence, seeing such a primitive issue in Windows 11 seems almost uncharacteristic. However, this issue was found in an early build of Windows not meant for the public so it’s not as problematic. If anything, this makes Microsoft aware of the issue which allows them to remove it early on in Windows 11’s life and make sure it never surfaces after its public release.

Windows Defender Has Had A Rocky Start

Windows 11 has been plagued with several issues pertaining to Windows Defender since the very first preview build was released. Case in point, many users reported that they had to turn on Real-time protection in Windows Defender each time they turned on their system. Another issue was with Automatic Sample Submission, the service that automatically sends data to Microsoft’s servers when it detects an anomaly such as a virus in your system, to turn off after every system restart.

These issues, along with some others, are also scattered throughout the user base of Windows 11 and don’t affect everyone and since these are older, too, so they’ve been likely resolved or patched by Microsoft by now. The Windows Defender issue, however, is new and hasn’t been patched yet. As mentioned earlier, thankfully, there is an easy solution to counter the issue.

The Fix To Windows Defender’s Pop-Up Issue

  • Press the Windows key,
  • Type “PowerShell”,
  • Right-click on Windows PowerShell and click “Run as administrator”,
  • Copy the following command, paste it in PowerShell and press Enter.
Get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage

The command will run and fix the issue. Now, when you click on the Open Windows Security Button in Windows 11, instead of giving you a pop-up asking to select an app to open Windows Defender, it will simply open as usual.

Huzaifa Haroon
Born and raised around computers, Huzaifa is an avid gamer and a Windows enthusiast. When he's not solving the mysteries of technology, you can find him writing about operating systems, striving to inform the curious.