[Fix] “This Connection is Untrusted” Problem with Google and Other HTTPS Websites in Mozilla Firefox

Recently one of AskVG's active readers "TheAslan" contacted me regarding a weird problem in Mozilla Firefox web browser. Whenever he tried to open Google, YouTube and other Google related websites in Firefox, her received following error message:

This Connection is Untrusted

You have asked Firefox to connect securely to www.google.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.

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.

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)


After some troubleshooting, he was able to find out the culprit. It was happening due to Kaspersky security program which was blocking HTTPS websites due to a certificate related issue. There was also a thread at official Kaspersky Lab forums regarding the same problem and a user was having similar problem while trying to access Google and Bing websites. Kaspersky staff member told the reason as following:

This untrusted connection issue might appear if you are using a 64-bit version of Mozilla Firefox along with Kaspersky security suite. Since Firefox 64-bit version is very new, there is no support for it yet in Kaspersky program. That's why it might show that error message when you try to open HTTPS websites in Firefox 64-bit version.

If you are also using Mozilla Firefox 64-bit version and Kaspersky antivirus or Internet security suite in your computer, you might also face this problem. If you face this problem, you can try following solutions:


Since 64-bit version of Firefox is not yet supported by Kaspersky, you can try to uninstall Firefox 64-bit and then install the regular 32-bit version of Firefox and your problem will be solved.


If you want to keep using 64-bit version of Firefox, then you'll need to manually install Kaspersky antivirus root certificate in Firefox to fix this issue.

Follow these simple steps:

1. Open Firefox Preferences window and go to Advanced section. Now click on Certificates tab.

2. Under Certificates tab, click on "View Certificates" button.


3. It'll open Firefox Certificate Manager window. In Authorities tab, click on Import button.


It'll open a browse window to select the file containing CA certificate to import.

4. Now copy following path and paste it in the addressbar or file name text box of the browse window:

C:\ProgramData\Kaspersky Lab\AVP16.0.0\Data\Cert

5. Now press Enter key and the browse window will open Cert folder. Now select "(fake)Kaspersky Anti-Virus Personal Root Certificate.cer" file and click on Open button.


6. Firefox will show a confirmation window, enable all 3 checkboxes present in the window such as Trust this CA to identify websites, email users and software developers.


Now click on OK button to apply changes.

That's it. Now try to open Google and other HTTPS websites and Firefox will open them fine without any problem.


The next update of Kaspersky should automatically fix this issue and should include support for Firefox 64-bit version.

Also Check:

[Fix] SSL Error or Invalid Security Certificate Problem in Facebook or Other Websites

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Posted in: Gadgets & Internet, Mozilla Firefox, Troubleshooting

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  • I was also getting this issue when I upgraded to Windows 10. (I believe I just had Windows Defender installed.) It fixed itself in time, though.

  • I have the same issue without Kaspersky Antivirus. I use ESET NOD32 and I can't find any certificates to install in Firefox 32-bit.

  • This Connection is UNTRUSTED in FireFox I noticed has been caused by ADGUARD 5.0 and 6.0. After going through all the mozilla help/tutorials the only solution I found was to uninstall adguard remove the firefox profile and do a clean install of firefox and then reinstall adguard. I elected not to have aduard filter mozilla instead I use ublock origin. Adguard is great for Edge and IE but I have found it can or may cause problems with mozilla. I am not as tech savvy as you gentlemen but I hope this may help point someone in the right direction.

  • Thanks For the Fix :)

  • Had been bugging me for a while this problem. Finally fixed with this solution. Thanks a bunch!

  • I have just renewed my Kaspersky subscription and this has created the same problem for me, although its OK if I use I.E.
    I followed your tutorial and it now works perfectly, so thank you for you invaluable assistance.

  • All i had to do is change my date and time.

  • Hi

    I am using a virtual pc at work and the pc does not have Kaspersky antivirus, can you please advise how to fix this error? Thanks.

  • Ademola Onasoga.

    Thank you very much, I tried everything, I even desintalled my firefox and my kaspersky it did not work.
    The solution was there, I had just to change the time and date and it works.

    thank you very much

  • Thanks! Just used your instructions.

  • I have an old Windows XP computer that had the Firefox "your connection is not secure" error. It turned out the computer had the wrong date. I changed the date, and it is fine. I had to replace the batter on the I/O board years ago, so it is possible it needs a new battery again.

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