Mozilla Firefox Displaying Certificate Error Page

PKI Tutorials - Herong's Tutorial Examples

∟Mozilla Firefox Displaying Certificate Error Page

This section provides a tutorial example showing that Mozilla Firefox fails to validate an HTTPS server certificate and displays a certificate error page.

Now I want to see how Mozilla Firefox behaves after I deleted the root certificate "VeriSign Class 3 Public Primary Certification Authority - G5".

1. Open Mozilla Firefox to visit "https://login.yahoo.com".

2. Mozilla Firefox returns with an untrusted connection error page:

Certificate Error Page in Mozilla Firefox 61 — Showing Certificate Validation Error in Mozilla Firefox 61

3. Read the error message:

This Connection is not secure

The owner of login.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.

Mozilla Firefox fails to validate "login.yahoo.com" certificate as expected, because the root CA "VeriSign Class 3 Public Primary Certification Authority - G5" certificate has been deleted from Firefox.

If you are using an older version, the error message may read differently as shown below:

This Connection is Untrusted

You have asked Firefox to connect securely to login.yahoo.com, 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.

Get me out of here!

Technical Details

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