Firefox Error: “Software is Preventing Firefox From Safely Connecting to This Site”

This article explains how to fix a specific error that prevents Firefox from displaying pages due to Sophos preventing the connection.

 Issue

When opening Firefox, the following error message is displayed:

 Resolution

2. Open Firefox.

3. In the address bar, type about:config and press Enter.

4. When asked to “Accept the Risk and Continue," agree to it.

5. In the preferences bar, type Security.pki.mitm_canary_issuer and press Enter.

6. Click the pencil icon next to the entry and delete the entire line.

7. Close and relaunch Firefox. Open a webpage to check if the error is resolved.