And for developers: https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Rel... The biggest change from my perspective is "Firefox now ensures that localhost URLs — such as http://localhost/ and http://dev.localhost/ — refer to the local host's loopback interface (e.g. http://127.0.0.1 ). As a result, resources loaded from localhost are now assumed to have been delivered securely (see Secure contexts), and also w…
Am I incompetent if I thought all browsers all did this already by default? Or was this typically enforced at the OS/networking-stack level, and now Firefox is adding an additional guarantee that it will happen directly in the browser, even if the networking stack would say otherwise?
In the new setup proxies can't proxy localhost unless you set a pref to explicitly let them do that, and for "localhost" and hostnames ending in ".localhost" Firefox won't even ask the DNS stack for the IP, assuming loopback instead.