Firefox used to have a preference you could set: security.warn_submit_insecure When set to true, Firefox would warn the user that the data they were about t

Firefox used to have a preference you could set: security.warn_submit_insecure When set to true, Firefox would warn the user that the data they were about to send was not encrypted and would be sent over plain-text HTTP. This setting was removed at some point (FF19, IIRC) and is currently (AFAICT) a NOP; cf. bug #799009, "Remove support for obsolete SSL-related warning prompts" [0] [0]: https://bugzilla.mozilla.org/show_bug.cgi?id=799009 https://bugzilla.mozilla.org/show_bug.cgi?id=799009