This is about network detection done by Firefox on startup. See Network Detection: *https://support.mozilla.org/en-US/kb/how-stop-firefox-making-automatic-connections You can set <b>network.captive-portal-service.enabled = false</b> on the <b>about:config</b> page to disable this feature. You can open the <b>about:config</b> page via the location/address bar. You can click the button to "Accept the Risk and Continue". *https://support.mozilla.org/en-US/kb/about-config-editor-firefox