exploit.js

var socket = null;
var lastDataSent = null;
var using = null;

let iframe = document.createElement("iframe");
document.body.appendChild(iframe);
window.open = iframe.contentWindow.open.bind(window);

var hw = prompt("Paste url here", "https://www.gimkit.com/join");

let win = window.open(hw);
//alert(win);
const nativeSend = win.WebSocket.prototype.send;
win.WebSocket.prototype.send = function(data) {
    nativeSend.call(this, data);
    var enc = new TextDecoder("utf-8");
    lastDataSent = data;

    socket = this;
};

setInterval(() => {
    win.document.onkeydown = (e) => {
        if (e.repeat) {
            return;
        }
        if (e.key == ";") {
            using = lastDataSent;
            win.alert("Saved.");
        } else if (e.key == "u") {
            if (using) {
                socket.send(using);
            };
        };
    };
});
win.alert("Started.");
document.write("Keep this tab open. Close tab to stop hacks.");