Don't panic yet. This message can appear if some files are dropped in the Firefox program folder and/or subfolders. Let's see what we can discover.

First, could you open the About Policies page: type or paste about:policies in the address bar and press Enter to load it. Normally this page reports: "The Enterprise Policies service is inactive." Does yours show any active policies? If so, what are they?

Thank you. Here's what comes up- Certificates ImportEnterpriseRoots true

This is likely because your Avast security software is trying to inject itself in the certificate chain to be able to intercept your internet traffic. You can either accept this or disable this feature to scan HTTPS traffic in Avast.

• https://support.mozilla.org/en-US/kb/error-codes-secure-websites

There is likely a policy active to import the OS certificates. The System Details list shows :

• policiesStatus: 1
• security.enterprise_roots.enabled: true

You can check the about:policies page (63+) what policies are active.

• https://support.mozilla.org/en-US/kb/see-active-policies-firefox-enterprise

Got it. Thanks!

Works for me. see screenshot You already tried Firefox in Safe Mode and Nightly is from Mozilla? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf

You have current ffmpeg and libav files. see screenshot