Are you talking about an app on the computer or the website?

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Thank you!

Please explain the problem in detail. What happens? What is the exact error messages?

Google is typical of a number of websites I try to use. I get the response as shown in the attached image. I have tried a number of suggested solutions, none of which solve the problem. It seems to be its https sites that are blocked, though bbc.co.uk, which is set as the home page, is not, as it is accessed in a different way. Although I prefer FIREFOX I am using CHROME as it does not have this problem. I am using Windows 7 and have the latest version of Firefox. I also have a Windows 10 PC with FIREFOX and BITDEFENDER but this works fine.

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

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

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

• MOZILLA_PKIX_ERROR_MITM_DETECTED
• 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

BitDefender sets up as a "man in the middle" of your browsing. In order to read secure connections, it needs to issue fake site certificates. Firefox knows they not genuine. To set up Firefox to trust Bitdefender to issue fake site certificates, try the steps in the following post provided by another user who got them from Bitdefender support:

https://support.mozilla.org/questions/1238264#answer-1168921

Any improvement?

This did not solve the problem but it gave me the drive to have another go at BITDEFENDER with the following result, which has now solved the problem.

Dear Brian,

Before anything else please allow us to apologize for the delayed response.

Do you happen to have a master password enabled in your Firefox settings? This is a common cause as it corrupts the Bitdefender certificate that allows scanning https sites.

Please access the link below: https://support.mozilla.org/en-US/kb/use-master-password-protect-stored-logins

Scroll down to the section "Removing the master password" and follow those steps to remove the master password feature.

Then: 1. Exit (close) Mozilla Firefox, then open Command Prompt. [How to open Command Prompt] https://www.wikihow.com/Open-the-Command-Prompt-in-Windows

2. In the black command prompt window type the following line and press Enter on your keyboard

        start firefox -P

3. A box appears on your screen. Click on "Create Profile" then wait a couple of minutes. 4. Repeat the command from step 1 and this time select the newly created profile then choose to delete it. 5. Open Firefox and check if the web pages load fine now.

We will set this ticket to a pending state, waiting for your answer.

Best Regards, Eva Chaps Bitdefender Support Team

It sounds as though BitDefender wants you to choose between using their filter and protecting your passwords stored on disk. Each has its risks, so that is your call.