Recommended read for more trick: https://mksben.l0.cm/2020/10/discord-desktop-rce.html?m=1​

When I test Electron app, first I always check the options of the BrowserWindow API, which is used to create a browser window. By checking it, I think about how RCE can be achieved when arbitrary JavaScript execution on the renderer is possible. Example:

const mainWindowOptions = {
  title: 'Discord',
  backgroundColor: getBackgroundColor(),
  width: DEFAULT_WIDTH,
  height: DEFAULT_HEIGHT,
  minWidth: MIN_WIDTH,
  minHeight: MIN_HEIGHT,
  transparent: false,
  frame: false,
  resizable: true,
  show: isVisible,
  webPreferences: {
    blinkFeatures: 'EnumerateDevices,AudioOutputDevices',
    nodeIntegration: false,
    preload: _path2.default.join(__dirname, 'mainScreenPreload.js'),
    nativeWindowOpen: true,
    enableRemoteModule: false,
    spellcheck: true
  }
};

nodeIntgration RCE

If the nodeIntegration is set to true, a web page's JavaScript can use Node.js features easily just by calling the require(). For example, the way to execute the calc application on Windows is:

<script>
  require('child_process').exec('calc');
</script>

Read Arbitrary Internal FIle

If contextIsolation set to false you can try to use <webview> (similar to <iframe> butcan load local files) to read local files and exfiltrate them: using something like <webview src=”file:///etc/passwd”></webview>:

(Trick copied form here).