Hi DoktorNietzsche, a common reason for this would be Firefox not being set up to trust the fake site certificates generated by Bitdefender. In order for Firefox to accept those, Bitdefender's certificate needs to be installed in each Firefox profile. I think it might check whether it needs to do that at Windows startup, but if it didn't happen automatically, it's possible your wife will need to use a feature in Bitdefender or import the certificate into Firefox manually. Could you check with Bitdefender documentation or support on whether they have the current steps for that? It can be difficult to wade through all the threads here.

I have the free version of Bitdefender, and it doesn't have any buttons or screens or anything related to certificates (there are hardly any controls on it at all). There also doesn't seem to be any official tech support for the free version. I figured out how to manually import a certificate into Firefox, but I do not know from where to get the certificate so that I can import it.

You can check if there is more detail available about the issuer of the certificate.

• click the "Advanced" button show more detail
• click the blue error text (SEC_ERROR_UNKNOWN_ISSUER) to show the certificate chain
• click "Copy text to clipboard" and paste the base64 certificate chain text in a reply

If clicking the blue error text doesn't provide the certificate chain then try these steps to inspect the certificate.

• open the Servers tab in the Certificate Manager
  • Options/Preferences -> Privacy & Security
    Certificates: View Certificates -> Servers: "Add Exception"
• paste the URL of the website (https://xxx.xxx) in it's Location field

Let Firefox retrieve the certificate -> "Get Certificate"

• click the "View" button and inspect the certificate

You can find detail like the issuer of the certificate and intermediate certificates in the Details tab.

• https://support.mozilla.org/en-US/kb/error-codes-secure-websites

DoktorNietzsche said

I figured out how to manually import a certificate into Firefox, but I do not know from where to get the certificate so that I can import it.

Conveniently, you can export it from your working profile and then import it into your non-working profile. The trick is finding it. Most likely it is under Bitdefender? Please check on the Options/Preferences page:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the search box at the top of the page, type cert and Firefox should filter to the Certificates section. Then click the "View Certificates" button. Check the "Authorities" tab and scroll down to see whether Bitdefender is listed with its certificate. Click the certificate to enable the Export button.

I tried reinstalling Bitdefender, and I am having the same problem, but now it is a mozilla pix something error. I am going to try getting rid of Bitdefender, switching the Windows Defender on, and see if it happens then.

Sorry, that was mozilla kpix (not pix, that was autocorrect)

Okay, so I held off on the plan to uninstall Bitdefender. I had already started typing that message when jscher2000's most recent comment popped up. I was able to find the cert in my account, save it to my desktop, and then import it into my wife's, and that seems to have done it. Thanks for the help!