Error message: (Error code: sec_error_unknown_issuer)

When you get this for pretty much all secure sites, the problem usually is one of the following:

(1) Error in your system's date, time, or time zone, which throws off certificate validity checks. Sometimes allowing computers to use an internet-based time source can introduce this problem.

(2) Firefox not being set up to work with your security software that intercepts and filters secure connections. Products with this feature include Avast, BitDefender, ESET, and Kaspersky; AVG has a Search Shield feature which can cause this error on search sites.

(3) On Windows 10, Firefox not being set up to work with the parental control software Microsoft Family Safety.

(4) Malware on your system intercepting secure connections.

So... which is it?

If you have any of those specific security products, that would be the first thing to check. We might be able to assist with specific next steps based on what you have if you tell us.

To investigate further, you could inspect the certificate for a site that doesn't use HSTS. That could either be a site for which you already added an Exception, or another site. Here's an example using my test page:

https://jeffersonscher.com/res/jstest.php

You likely will get an error page. Expand the "I understand the risks" section and look for an Add Exception button.

Note: You don't need to complete the process of adding an exception -- I suggest not adding one until we know this isn't a malware issue -- but you can use the dialog to view the information that makes Firefox suspicious.

Click Add Exception, and the certificate exception dialog should open.

Click the View button. If View is not enabled, try the Get Certificate button first.

This should pop up the Certificate Viewer. Look at the "Issued by" section, and on the Details tab, the Certificate Hierarchy. What do you see there? I have attached a screen shot for comparison.

Hello jscher,

The issuer I see for that site is the same as the one in your screenshot. However, I do not get the "Untrusted" popup when attempting to visit the site. I have to manually view the certificate.

I don't have any other Anti-virus software other than Window's built-in security software.

I don't have Windows 10, but I do have Family Safety enabled.

My laptop's date and time are accurate. Can't seem to find a date and time setting in Firefox itself.

If the problem doesn't occur on my site (?!) maybe you can use this internal page to view the certificate for Google, Bing, or YouTube:

chrome://pippki/content/exceptionDialog.xul

Paste that in the address bar and press Enter to load the page.

Then try pasting in https://www.bing.com/ and click Get Certificate. If possible, then click View. Anything unusual in the Issued By area?

If Firefox doesn't allow checking the certificate, try another browser. Usually clicking the padlock icon in the address bar will show a link to view the certificate. On Chrome, you first need to click Connection on the drop-down.

If Family Safety turns out to be the issue, please see this thread for how to set up Firefox to work with the program: Firefox has problems with security certificates for yahoo and google when my son logs in as a child under a family account in windows 10.

Thank you very much. It now works as it should.

AppleAddikt said

Error message: (Error code: sec_error_unknown_issuer)

I have this problem... not only for google, but also with the mozilla support site when I tried to change my password using firefox. I used chrome to get it changed!! My date / time is correct... I've tried the file delete when firefox is closed... I ran norton... some sites work, ie... weather.com.. many others do not. sometimes i get the 'add exception', other times I do not. Google.com is the most irritating, but not only problem.. two days ago all seemed well. I saw the suggestion to right click the frame.. but have no idea what a frame is.. or where i can find it to right click..

need a SIMPLE solution.. what if I removed firefox and redownloaded?? note that IE and Chrome are working without problem.. Firefox is working on my laptop, but not my desktop.. Feel it is something in my firefox that has changed... but what???

thanks,

Hi georgehamilton71, sorry for the lack of reply, but this thread was already marked solved last Fall. If you still have this issue, could you start a new question?

https://support.mozilla.org/questions/new/desktop/

Scroll down past the suggestions if they are not on point to continue with the form.