I have followed the steps to correct my 'sec_error_unknown" issue including reinstalling, still get the message and can't open any site, including Mozilla!
Please help, I am about to lose my mind!! I have tried every troubleshooting idea from Mozilla, including uninstalling and reinstalling Firefox. Every site I go to I get the following message:
"The owner of mail.yahoo.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.
This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate."
When I click on Advanced I see this:
mail.yahoo.com uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. Error code: SEC_ERROR_UNKNOWN_ISSUER
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There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate.
- uses an invalid security certificate SSL_ERROR_BAD_CERT_DOMAIN
- configured their website improperly
How to troubleshoot the error code "SEC_ERROR_UNKNOWN_ISSUER" on secure websites https://support.mozilla.org/en-US/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER
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