You may receive the below error in FireFox when attempting to add a SSL certificate security exception. If you do follow the below steps to be able to actually add the security exception.

Error: uses an invalid security certificate.
The certificate is not trusted because it is self signed.
(Error code: sec_error_untrusted_issuer)

Image of Error:

FireFox Error: sec_error_untrusted_issuer

Follow these steps to add an SSL certificate security exception in FireFox.

  1. Visit URL: Visit the HTTPS URL in question. For example You will come to a page that looks like the below image.

    FireFox: Secure Connection Failed

  2. Click Link: Click the “or you can add an exception” link at the bottom of the white box. This will display two buttons at the bottom as shown in the below image.

    FireFox: Add Exception

  3. Click Add Exception: Now click the Add Exception button which will open a new window as shown below.

    FireFox: Get Certificate

  4. Modify Location: Now here is where a lot of people run into the issue. They attempt to Get Certificate without adding the port number. So modify the location by adding “:443″ to the end. Your new Location would look like
  5. Click Get Certificate: Now click the Get Certificate button which will now provides functionality to the Confirm Exception button as shown in the below image.

    FireFox: Confirm Security Exception

  6. Confirm Exception: Now click the Confirm Exception button located at the bottom of the window. Once clicked you will be redirected to the page you initially attempted to visit. All future visits to the page will direct you right to the page without having to add the certificate every time.

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12 Responses to “FireFox: Error code: sec_error_untrusted_issuer”
  1. Robert says:

    Thanks! I didn’t think about adding the 443. As it is when browsing, 443 should be the default.


    alex Reply:

    Yeah… I still don’t know why 443 is required because it should be implied by HTTPS. No telling… it works. :)


  2. Stephen says:

    I’ve tried adding the exception, with the port, and am still getting the error. I’m using Firefox 3.0.10 on a Max running OSX 10.5.7.



    alex Reply:

    Hello Stephen,

    Even though you get another error when you view the certificate… have you tried to just go ahead and confirm the exception any way? I just tested and its possible it appears you cannot confirm it when you actually can. Also I believe Firefox 3.0.11 is out so you may want to upgrade to the latest version as well.


  3. fili says:

    Thanks for having shared this. I was also missing the :443


    alex Reply:

    Hello fili,

    No problem. Glad it helped you out. It seems odd that adding :443 to specify the HTTPS port is required but hey whatever works!



  4. Dominatrix says:

    Very helpful indeed…thank you!!


    alex Reply:

    Hello Dominatrix,

    I wasn’t aware that Firefox SSL topics were appealing to dominatrix… I think I may have learned more than you on this one… so umm.. thx?



  5. ruth says:

    quero a sesar minha conta internete


    alex Reply:

    Hello ruth,

    Not sure what you are asking or saying…



  6. zeroday1 says:

    Why…Oh Why…should we even need to consider making such an exception…when it’s quite possible that it is a maintenance issue with the website itself…hence the error code denoting an invalid certificate!

    Should we automatically assume that every single website address is up to par in this regard?…

    I think NOT!

    Sometimes we have to resolve ourselves to the fact that if a website renders such an error, it is because there is an inherent flaw with there current security protocols…and therefore we should be extra careful and in fact, maybe even stay away from the site for now…until, that is, the website owner has addressed the problem.

    No sense in creating further security risk by insisting on visiting the site without first at least finding out why the problem is occurring and also what the site owner is saying about the error.

    All the top browsers are far more advanced than they used to be…and so long as the browsers are up to date, as well as your computer security software and properly configured, then chances are good that it is a website problem that should not be obfuscated by the average end-user by making a security exception (UNLESS YOU ARE AN EXPERT AND KNOW EXACTLY WHAT YOU ARE DOING)…otherwise you just create a security risk that you may later regret…

    It is important to understand the functionality and features of the web browser you use.

    Enabling some web browser features may lower security. Often, vendors will enable features by default to improve the computing experience, but these features may end up increasing the risk to the computer.

    Attackers focus on exploiting client-side systems (your computer) through various vulnerabilities. They use these vulnerabilities to take control of your computer, steal your information, destroy your files, and use your computer to attack other computers. A low-cost way attackers do this is by exploiting vulnerabilities in web browsers. An attacker can create a malicious web page that will install Trojan software or spyware that will steal your information.

    Additional information about spyware is available in the following document:

    Rather than actively targeting and attacking vulnerable systems, a malicious web site can passively compromise systems as the site is visited. A malicious HTML document can also be emailed to victims. In these cases, the act of opening the email or attachment can compromise the system.

    Some software features that provide functionality to a web browser, such as ActiveX, Java, Scripting (JavaScript, VBScript, etc), may also introduce vulnerabilities to the computer system. These may stem from poor implementation, poor design, or an insecure configuration. For these reasons, you should understand which browsers support which features and the risks they could introduce. Some web browsers permit you to fully disable the use of these technologies, while others may permit you to enable features on a per-site basis.

    Understanding what different features do will help you understand how they affect your web browser’s functionality and the security of your computer.

    The above information was excerpted from the following webpage:


  7. madan says:



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