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This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox only connect to it securely. As a result, it is not possible to add an exception fo

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  • Last reply by jscher2000

I am unable to use Firefox since installing the new version. On almost every website I receive this error message: This Connection is Untrusted

You have asked Firefox to connect securely to, but we can't confirm that your connection is secure.

Normally, when you try to connect securely, sites will present trusted identification to prove that you are going to the right place. However, this site's identity can't be verified. What Should I Do?

If you usually connect to this site without problems, this error could mean that someone is trying to impersonate the site, and you shouldn't continue.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox only connect to it securely. As a result, it is not possible to add an exception for this certificate. 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)

I have never encountered this error before, can you help please? My system is: Win 7 Pro SP1 i7-390X CPU @ 3.3GHz 32Gb RAM 64 bit OS

All Replies (3)

I might first try safe mode: Diagnose Firefox issues using Troubleshoot Mode

Do you use an antivirus or firewall?

You can check if where the certificates are issued by with these instructions:

Check to make sure that the certificate is secure:

If you can't inspect the certificate via "I Understand the Risks" then try this:

Open the "Add Security Exception" window by pasting this chrome URL in the Firefox location/address bar and check the certificate:

  • chrome://pippki/content/exceptionDialog.xul

In the location field of this window type or paste the URL of the website.

  • retrieve the certificate via the "Get certificate" button
  • click the "View..." button to inspect the certificate in the Certificate Viewer

You can inspect details like the issuer and the certificate chain in the Details tab of the Certificate Viewer. Check who is the issuer of the certificate. If necessary then you can attach a screenshot that shows the certificate viewer.

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

During your update, did the Firefox Refresh feature run? The telltale sign is that an Old Firefox Data folder would now appear on your desktop, and inside would be a semi-randomly-named folder with files that were last modified just around the time of your update. If you find that folder, hang onto it in case you notice important data missing from your Firefox.