Discord Javascript & CSS Injector

.env

PORT=31337
APPLICATION_ID=1337

README.md

Set up

Make sure to start Discord like this

C:\Users\user\AppData\Local\DiscordCanary\app-1.0.37>DiscordCanary.exe --remote-debugging-port=31337

How this works

Discord is a webapplication ported to desktop by using electron. Thus discord uses chrome and chrome comes with a built-in devtool tab. This script communicates with websockets to the remote-debugging-port to discord. Its able to execute Javascript leading to injections of all sorts and kinds

discordcssinjector.py

import websocket
import json
import requests
import os
import logging
import subprocess

from dotenv import load_dotenv

load_dotenv()

logging.basicConfig(level=logging.INFO)

class DataManager:
    def __init__(self, port):
        self.port = port
        self.application_id = int(os.environ["APPLICATION_ID"])

    def prepare_payload(self, method="Runtime.evaluate", **params):
        logging.info("Preparing Payload")
        return {"id": self.application_id, "method": method, "params": params}

    def retrieve_websocket_debugger_url(self):
        logging.info("Retrieving Websocket Debugger URL")
        logging.info(f"Requesting http://localhost:{self.port}/json")

        try:
            r = requests.get(f"http://localhost:{self.port}/json")
        except requests.exceptions.ConnectionError:
            logging.critical("There is not Debugger Information Data present. Try to restart the application and check your port again (.env file)!")
            return exit(0)

        try:
            data = r.json()
        except json.JSONDecodeError:
            logging.critical("Debugging Information seems to be corrupted. Please try again or try to restart the application and check your port again (.env file)!")
            return exit(0)

        if not data:
            logging.critical("Couldn't find debugger information. Try to restart the application and check your port again (.env file)!")
            return exit(0)

        data = data[-1]

        logging.info("Websocket Debugger URL is: " + data["webSocketDebuggerUrl"])

        return data["webSocketDebuggerUrl"]


class DiscordInjector:
    def __init__(self):
        self.__port = os.environ["PORT"]
        self.__dm = DataManager(self.__port)
        self.__debugger_url = self.__dm.retrieve_websocket_debugger_url()

        logging.info("Setting up Websocket Connection")
        self.__ws = websocket.create_connection(self.__debugger_url)
        logging.info("Connected to Websocket")

    def inject_javascript(self, javascript):
        logging.info("Preparing Javascript Oneliner")

        payload = self.__dm.prepare_payload(expression=javascript)
        self.__inject_payload(payload)

    def inject_javascript_file(self, path):
        logging.info("Reading Javascript File")

        with open(path, "r") as fh:
            data = fh.read()

        self.inject_javascript(data)

    def __inject_payload(self, payload):
        logging.info("Injecting Payload")
        self.__ws.send(json.dumps(payload))

    def test_injection(self):
        logging.info("Testing Injections")
        self.inject_javascript("alert('Hello from DiscordCSSInjector made with Python!');")


if __name__ == '__main__':
    # C:\Users\user\AppData\Local\DiscordCanary\app-1.0.37>DiscordCanary.exe --remote-debugging-port=31337
    # You have to run discord like the above in order to get chrome devtools to work
    injector = DiscordInjector()
    injector.inject_javascript_file("./test_script.js")
    # injector.inject_javascript("console.log('1');")
    # injector.test_injection()

test_script.js

console.log("Custom JavaScript injected");

let head = document.getElementsByTagName("head")[0];

let test = document.getElementsByClassName("python-discord-injector");
if (test.length > 0) {
    head.removeChild(test);
}

let style_elem = document.createElement("style");
style_elem.classList.add("python-discord-injector");

style_elem.innerHTML = `
.theme-dark {
    --header-primary: rgba(255, 255, 255, 0.719);
    --text-normal: #c4c4c4f1;
}
span.mention {
    color: rgb(255, 0, 0);
    background-color: rgb(100, 0, 0);
}
}`;

head.appendChild(style_elem);

test_style.css

.theme-dark {
    --header-primary: rgba(255, 255, 255, 0.719);
    --text-normal: #c4c4c4f1;
}

span.mention {
    color: rgb(255, 0, 0);
    background-color: rgb(100, 0, 0);
}