Greasy Fork is available in English.
firefox用
// ==UserScript==
// @name 按下alt时屏蔽点击
// @description firefox用
// @version 1.2
// @match *://*/*
// @namespace http://greasyfork.icu/users/12375
// ==/UserScript==
let alt = false;
document.addEventListener('keydown', e => alt = e.key === 'Alt');
document.addEventListener('keyup', () => alt = false);
// 新增窗口失焦监听
window.addEventListener('blur', () => alt = false);
document.addEventListener('click', e => alt && (e.preventDefault(), e.stopPropagation()), true);