Исправление MozillaFirefox, (текущая версия) :
whenever you enter an insecure (HTTP) URL in Firefox’s address bar, or you click on an insecure link on a web page, Firefox will now first try to establish a secure, encrypted HTTPS connection to the website
То есть, при явном указании HTTP будет попытка проапгрейдить до HTTPS.
Исходная версия MozillaFirefox, :
whenever you enter an insecure (HTTP) URL in Firefox’s address bar, or you click on an insecure link on a web page, Firefox will now first try to establish a secure, encrypted HTTPS connection to the website