If you are using Windows and Internet Explorer, the browser generates this error when it attempts to open a website that has a problematic security certificate.

If Windows Security (Microsoft Defender) throws Error 8024402f, Protection definition update failed on Windows 11, then follow this post to successfully fix the issue.

Microsoft has fixed CertificateServicesClient issue that was causing error events to appear in the Windows Event Viewer after ...

Microsoft's latest Windows update for Windows 11, Windows 10 is causing unintended UAC prompts to appear in certain cases for non-admin users.

Microsoft says the August 2025 security updates are triggering unexpected User Account Control (UAC) prompts and app ...

If you are not able to open Windows Security & you see error: Cannot Open this app, Your IT administrator has disabled Windows Security, see this post.

Next, check for any pending Windows updates. Outdated Windows, especially if you have opted for the Windows Insider Program, can lead to errors like Kernel Security Check Failure.

Microsoft has patched an Event Viewer bug impacting Windows 11, version 24H2 customers. However, the fix will be rolled out ...

Users repeatedly report that "Windows Security" no longer starts. As this virus protection is integrated, this error should be rectified immediately.