PoC discord realtime message decryption engine

DiscordCrypt.js

(() => {
  let styles = `
    .un-decryptable,
    .encrypted-msg {
      background-color: rgba(255, 141, 0, 0.29);
      padding: 5px;
      border-radius: 5px;
    }
    .un-decryptable::before,
    .encrypted-msg::before {
      content: "Decrypted message: ";
      display: block;
      font-weight: bold;
      padding-bottom: 10px;
      margin-bottom: 10px;
      border-bottom: 1px solid rgba(255, 255, 255, 0.39);
    }
    .un-decryptable {
      background-color: rgba(255, 0, 0, 0.29)
    }
    .un-decryptable::before {
      content: "Failed to decrypt message!";
    }
  `
  let css = document.createElement('style')
  css.innerHTML = styles
  document.head.appendChild(css)
})();

function decrypt() {
  let prefix = `[ENCRYPTED]`
  let messages = document.getElementsByClassName('markup')
  for (let i = 0; i < messages.length; i++) {
    let message = messages[i].innerHTML
    if (messages[i].classList.contains('un-decryptable')) return
    if (message && message.startsWith(prefix)) {
      let decrypted = message.replace(prefix, '')
      try {
        decrypted = atob(decrypted)
        messages[i].classList.add('encrypted-msg')
        messages[i].innerHTML = (
          decrypted
          .replace(/&/g, '&amp;')
          .replace(/>/g, '&gt;')
          .replace(/</g, '&lt;')
          .replace(/"/g, '&quot;')
        )
      } catch(e) {
        messages[i].classList.add('un-decryptable')
        return
      }
    }
  }
}

clearInterval(window.discordCrypt)
window.discordCrypt = setInterval(decrypt, 1000)