How to Fix SEC_ERROR_UNKNOWN_ISSUER in Firefox
By Maya Hassan
· About Zone Desire
Quick answer
SEC_ERROR_UNKNOWN_ISSUER means Firefox does not trust who issued the website's certificate. It is often caused by antivirus HTTPS scanning. Turn off HTTPS scanning or allow Firefox to use Windows certificates, and check your date and time.
What does “SEC_ERROR_UNKNOWN_ISSUER” mean?
Firefox could not verify the certificate chain, so it shows "Warning: Potential Security Risk Ahead".
What causes it?
- Antivirus scanning HTTPS traffic
- Company network or proxy inspecting traffic
- Missing intermediate certificate on the site
- Malware
Steps to try
Stop when the issue is resolved.
- Set date and time to automatic.
- In your antivirus, turn off HTTPS/SSL scanning, or reinstall the antivirus to re-add its certificate.
- In Firefox, open about:config and set security.enterprise_roots.enabled to true.
- Restart Firefox.
- Scan the PC with Microsoft Defender.
Need more support? Check the official help: Google Chrome Help
FAQs
Why does Chrome work but Firefox does not?
Firefox uses its own certificate store, while Chrome uses the system store.
Should I add an exception?
Only on sites you own or fully trust, never on banking or login pages.