Firefox, an open-source web browser like its fellow web browsers is no exception to errors. It has been thriving as an alternative to many web browsers. Thus, users have an option to over browsers that suit their preferences. However, not everything about Mozilla Firefox is good. It is not immune to run time errors. The unknown server error in Firefox is implicative of an authentic server connection or server certificate that is not in conformity with other specifications of the Mozilla Firefox.

The SEC_ERROR _UNKNOWN ISSUER in Firefox can get on the nerves of the users which prompt them to leave the web browser and switch over.

You can be a frequent user of the Mozilla Firefox or you can resort to it when the default browser is out of place. Nonetheless.  won’t cost you anything to know the SEC_ERROR _UNKNOWN ISSUER in Firefox and how to

Fix SEC_ERROR _UNKNOWN ISSUER in Firefox right from scratch!


  • Because it lacks the essential certifications and evidence of security, the website is considered unsafe.
  • The website has an SSL certificate, which provides some level of online security and protection for sensitive information provided by users. The certificate, on the other hand, is self-signed, which means that the web browser will not trust such a certificate.
  • Another possibility is that the site visitor’s antivirus software on his machine has SSL scanning features activated, which might potentially be the source of the problem.

The most visible symptoms of the error can be a slow and unresponsive Mozilla Firefox putting all your surfing needs to halt. If you are in Mozilla Firefox searching

for something in the address bar, but instead of redirecting you to your desired webpage, it takes you to a blank page with an error message saying “Connection not secure in the middle. This is when your surfing experience becomes bitter and you change up your mind and switch over to another more spontaneous browser.


  • A virus scan is the first step to resolving the SEC ERROR UNKNOWN ISSUER problem. In cases when a website has been infected by a virus, this is essential. Viruses pose a threat because they prevent the Firefox browser from establishing a secure connection by obscuring the SSL certificate. Make sure that any viruses that were found during the virus scan are removed as quickly as feasible.
  • Mozilla’s SEC ERROR UNKNOWN ISSUER may also be fixed by creating new Firefox profiles. To begin the process of creating a new profile, please follow these instructions:
  • The first step is to launch Mozilla Firefox, then press the Menu button and choose Exit.
  • New User Profiles may be created.
  • The SEC ERROR UNKNOWN ISSUER problem might potentially be caused by antivirus software from a third-party vendor. Such software should be removed and replaced with a Microsoft antivirus programme like the Windows Defender if you are using it. It is possible to reinstall software if you do not wish to remove it. By re-installing the antivirus programme, the certificate may be included in Mozilla’s repository, which may help fix the problem altogether.
  • When traffic monitoring software changes its certificate, it may potentially disrupt secure connections. On HTTPS-encrypted websites, they may create problems. In this situation, the best course of action is to call an IT specialist who can come up with a workable solution.
  • You should disable SSL scanning in your antivirus programme. Your antivirus software may have prevented your PC from accessing a website that does not have a certificate issuer. Disable SSL scanning in your antivirus product as a first step in fixing the problem.
  • Make Sure Your Website Is Properly Setup.

    An intermediate certificate does not exist if a website visitor encounters a warning notice like the one shown in the error message: SEC ERROR UNKNOWN ISSUER. The “Advanced” option may be selected by certain users in order to proceed. Errors imply that the issuer CA is unknown, the server may not be sending the appropriate intermediate certificate, or an extra root certificate may be required if the certificate is present.

  • An unidentified third party is attempting to insert a certificate that Firefox does not trust, as seen by the SEC ERROR UNKNOWN ISSUER appearing on various web sites. A corrupted cert8.db file should be manually deleted as a precautionary measure in this case. The technique for deleting the cert8.db file is as follows:
  • If the SEC ERROR UNKNOWN ISSUER remains after attempting all of the aforementioned troubleshooting techniques, then you may add the web page to the Firefox exceptions list. “There is an “I understand the risk” button that you must press. Then, choose the option to add an exception. In the pop-up box that displays, click the button labeled “Confirm security exception.” After adding the page to the exception, the page will open without any issues.

With any luck, the information in this post will assist you in resolving the issue and allowing you to continue enjoying Mozilla Firefox to its full potential. To repair the problem of SEC_ERROR UNKNOWN ISSUER in Firefox, the aforementioned steps would be the perfect suit. If none of these steps fall in place, then resort to a simple restart of the system.