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"This connection is untrusted" - Firefox error message

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Error Messages

I am receiving the following error message in Firefox: uses an invalid security certificate.  Error message

After selecting Cancel to close the warning message, another error message is displayed:

This Connection is Untrusted error message


Install the MIT Certificate Authority

The error messages you are receiving are related to Firefox not recognizing MIT's certificate authority. In most cases, installing the MIT certificate authority (MIT CA) will resolve the issue.

  1. Download the MIT CA (Certificate Authority).
  2. Select Trust this CA to identify websites, and press OK.

  3. The CA should now be installed in Firefox. Try again to access the site.

If the error persists after installing the MIT Certificate Authority

This error should not occur for IS&T sites after the MIT CA (Certificate Authority) has been installed in the browser.

  • Make sure that you've typed the full name for the web server, for example, "", as opposed to "wikis".
  • Note that the MIT CA needs to be installed separately for each web browser that you use.
  • If you continue to get the error, contact the administrators for the site. They can let you know whether the following steps are needed for accessing the site:

(Note: follow these instructions only if you trust the administrator of the site.)

  1. Select Cancel to close the warning in the popup box. You may need to press Cancel multiple times.
  2. Select I Understand the Risks
    Result: An Add Exception button appears
  3. Select Add Exception
    Result: A message appears, "You are about to override how Firefox handles certificates"
  4. Press Get Certificate.
  5. Press Confirm Security Exception
    Result: A confirm window appears.
  6. Press Resend.
    Result: The site you are attempting to access should now be displayed.

Still having trouble?

This error can also occur when the MIT Certificate Authority is installed, but is not set to "identify websites." This setting is initially set when they install the CA, but also can be edited after the CA is installed. To edit the setting for the CA:

  1. Go to Preferences (Mac) or Options (Windows)
  2. Go to the Advanced tab > Encryption > View Certificates
  3. In the next window, go to Authorities and find the MIT CA.
  4. Highlight the MIT CA and select, Edit.
  5. Check the box to allow the CA to identify websites.

IS&T Contributions

Documentation and information provided by IS&T staff members

Last Modified:

July 28, 2016

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