I'm using firefox in linux for selenium test automation. Some of my automation tests need a sysproxy (provided by my company) to access internet. These prefs are set in my test "network.proxy.type": 1, "network.proxy.http": "company.proxy.com", "network.proxy.http_port": 8080 When firefox launches up, a prompt dialog is always shown asking for credentials for the proxy. I've added company .pem in path ~/.mozilla/certificates and these .pem are loaded correctly in firefox. Is there a way to disable the user prompt dialog?