What Does SEC_ERROR_UNKNOWN_ISSUER Error Mean? The SEC_ERROR_UNKNOWN_ISSUER error in Firefox indicates that the website's security certificate is not trusted. This usually happens when the certificate is self-signed, expired, or issued by an unknown certificate...
![What is Certificate Revocation List [CRL]?](https://sslinsights.com/wp-content/uploads/2024/01/certificate-revocation-list-crl.png)







