Simple steps, and the tools are free to use.

How to fix SEC_ERROR_UNKNOWN_ISSUER error in Mozilla Firefox

By | April 30, 2020

Do you experience the annoying “SEC_ERROR_UNKNOWN_ISSUER” error in Firefox? If you see the error: SEC_ERROR_UNKNOWN_ISSUER in Firefox, then Firefox tries to connect to a website that is not configured properly and only accepts HTST (HTTP Strict Transport Security) connections.

As a results it not possible to add an exception for this certificate.


In this article, I will give you instructions on how to fix the SEC_ERROR_UNKNOWN_ISSUER error in Firefox.

Read on and follow the step-by-step instructions.

How to fix SEC_ERROR_UNKNOWN_ISSUER error in Mozilla Firefox

Open the Firefox browser, in the address – navigation – bar type: about:config. Accept the risk and continue to the configuration settings in Firefox.

about config warning firefox

Search for value: security.enterprise_roots.enabled. Change security.enterprise_roots.enabled setting from False to True by double-clicking the security.enterprise_roots.enabled setting.

security.enterprise_roots enabled setting firefox

As you see it is fairly simple to fix the SEC_ERROR_UNKNOWN_ISSUER error message in Firefox. But hey! Who doesn’t like simple fixes?

Reload the website you were getting the SEC_ERROR_UNKNOWN_ISSUER from and try again. The SEC_ERROR_UNKNOWN_ISSUER error in Firefox is now gone!

Thank me! Help other people. Share this information on social media, a forum or website, and contribute to a safer internet for everyone.

Author: Max

Hi, I am Max. I am a computer security researcher. Every day I blog about new adware threats as they are released. I am also active in various online communities to help people with their computer problems. Stay safe!

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