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SEC_ERROR_UNKNOWN_ISSUER on a specif website only when using Quantum and Linux

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Firefox Quantum in Linux distros (tested on Debian and Mint) is refusing to open this website "https://www.mg.superesportes.com.br/". Its certificate is valid and it's not self signed like Firefox is saying. I can open it in any other browsers, and in Windows ,this problem doesn't exist.

"The owner of www.mg.superesportes.com.br 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."

Firefox Quantum in Linux distros (tested on Debian and Mint) is refusing to open this website "https://www.mg.superesportes.com.br/". Its certificate is valid and it's not self signed like Firefox is saying. I can open it in any other browsers, and in Windows ,this problem doesn't exist. "The owner of www.mg.superesportes.com.br 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."

Additional System Details

Application

  • User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0

More Information

FredMcD
  • Top 10 Contributor
4271 solutions 59908 answers

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

http://kb.mozillazine.org/Error_loading_websites


  • 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

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate. https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message https://support.mozilla.org/en-US/kb/connection-untrusted-error-message http://kb.mozillazine.org/Error_loading_websites *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

Question owner

FredMcD said

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate.

Like I said, I'm using Linux so I don't need and I don't use any security software. Besides, this problem is happening only with Firefox Quantum.

''FredMcD [[#answer-1112756|said]]'' <blockquote> There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate. </blockquote> Like I said, I'm using Linux so I don't need and I don't use any security software. Besides, this problem is happening only with Firefox Quantum.
cor-el
  • Top 10 Contributor
  • Moderator
17580 solutions 159053 answers

Try to rename the cert9.db (cert8.db.old) and cert8.db (cert8.db.old) files in the Firefox profile folder to remove intermediate certificates and exceptions that Firefox has stored.

If that has helped to solve the problem then you can remove the renamed cert8.db.old file.

Firefox will store intermediate certificates that a server sends in the Certificate Manager for future use.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

Try to rename the cert9.db (cert8.db.old) and cert8.db (cert8.db.old) files in the Firefox profile folder to remove intermediate certificates and exceptions that Firefox has stored. If that has helped to solve the problem then you can remove the renamed cert8.db.old file. Firefox will store intermediate certificates that a server sends in the Certificate Manager for future use. You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page. *Help -> Troubleshooting Information -> Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox