Here we can see “MOZILLA_PKIX_ERROR_MITM_DETECTED Error on Firefox”

Mozilla Firefox is still one of the most widely used web browsers. Its beta testers praised its security, quickness, and efficient add-ons. But, like other browsers, it has flaws. A lot of Firefox users have issues viewing websites with HTTPS prefixes, and most of them get these errors:


This indicates that your browser does not trust the certificates provided to websites you visit. The good news is that access is still possible. Here’s how to fix ‘MOZILLA PKIX ERROR MITM DETECTED.’

See Also:  How to Fix Firefox's 'SSL_Error_Bad_Mac_Alert' Error?


In this case, your network or system is interfering with your connection and certificates. As a result, Firefox distrusts certificates. This happens when malware tries to replace a genuine certificate with its own. To avoid this issue, you must have reliable security software installed on your computer.

There are several antivirus products available, but only Auslogics Anti-Malware offers comprehensive protection. It searches your browser extensions as well as your system memory for harmful apps, and it prevents data leaks and detects threats to your computer’s security.


Most impacted users said the issue happened on the Nightly version of Firefox. In this situation, use a stable build to access protected websites. If that doesn’t work, you can also discover how to fix security error codes on safe websites using Firefox. The methods are:

Method 1: Disable HTTPS Scanning

Any antivirus program’s security settings can be changed. So, if your security software scans HTTPS, turn it off. Many names, including: know this characteristic.

  • SSL Check
  • Don’t scan encrypted links.
  • Safe solutions

Method 2: Disabling HTTPS Scanning in Firefox

Disabling HTTPS screening in Firefox is not advised. For ‘MOZILLA_PKIX_ERROR_MITM_DETECTED’ errors, this is your last resort.

  1. Launch Mozilla Firefox.
  2. Enter “about:config” (no quotes) in the URL box.
  3. If an info message appears, select ‘I accept the risk!’
  4. Search for security.enterprise roots.enabled.
  5. Could you find it and double-click it?
  6. Set it to ‘true.
  7. Restart Firefox.

To import custom certificates from other security software products on your computer, follow the procedures above. As a result, the sources are now trusted, and the ‘MOZILLA_PKIX_ERROR_MITM_DETECTED’ error is gone.

See Also:  How to Resolve the Microsoft Edge Won't Open Issue

User Questions:

What should I do if I get a security certificate error message in Firefox?

  • Click Or you can add an exception on the error page.
  • Select Add Exception from the drop-down menu.
  • Select Get Certificate from the drop-down menu.
  • To view a window that outlines the problem with your z/OSMF site, click View.
  • Close the dialogue when you’ve checked the certificate.
  • To trust the z/OSMF site, click Confirm Security Exception.

How do I fix Firefox that does not resolve potential security issues?

  • Continue to use a shaky connection.
  • Add the site to your Trusted Sites List.
  • Disable your antivirus and firewall for the time being.
  • The SSL State should be cleared.
  • Clear Your History of Browsing
  • Allow Firefox to rely on root authorities.
  • Make a security setting change.

What is Mozilla_pkix_error_mitm_detected?

If you see the error code SEC_ERROR_UNKNOWN_ISSUER or MOZILLA_PKIX_ERROR_MITM_DETECTED when you click the Advanced button on a “Warning: Potential Security Risk Ahead” error page, it means the provided certificate was issued by a certificate authority that Firefox does not recognize and thus cannot be trusted.

What is the procedure for resetting Mozilla Firefox?

  • Open the “Settings” menu on your smartphone, then select “Apps.”
  • Locate and open the Firefox app.
  • Select “Storage” from the drop-down menu.
  • Select “Manage Space” from the drop-down menu.
  • “Clear all data” should be selected.
  • Tap “Ok” to confirm your decision.
See Also:  How to Fix: Microsoft Edge Update Installation Error STATUS_INVALID_IMAGE_HASH on Windows 10?

Why is Firefox oblivious to potential security flaws?

Firefox may detect that the website’s security certificate is expired or invalid due to inaccurate system date. Make sure your computer’s date, time, and time zone are right. See How to troubleshoot time-related problems on secure websites for additional details.