gm_fill_form

gm_fillform.js

// ==UserScript==
// @name        logon
// @namespace   https://www.formexample.com
// @include     https://www.formexample.com
// @version     1
// @grant       none
// @rut-at      document-start

const TIMEOUT = 2;
const NAME = "***";
const PASSWORD = "***";

document.addEventListener("load", function() {
    setTimeout(function() {
        document.querySelector("input[name=username]").value = NAME;
        document.querySelector("input[name=passcode]").value = PASSWORD;
        document.querySelector("input[name=passcode]").form.submit();
    }, TIMEOUT * 1000);
});