---
title: "Keep web content away from the operating · Agent Wranglers"
url: https://agentwranglers.se/playbook/desktop-apps/web-code-inside-desktop-apps/isolate-web-content
id: DSK-10
level: Required
risk: takeover
updated: 2026-10-22
tokens: 998
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Keep web content away from the operating system

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Web code inside desktop apps](https://agentwranglers.se/playbook/desktop-apps/web-code-inside-desktop-apps.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers.md). Updated 2026-10-22.

- ID: DSK-10
- Level: Required
- Chapter: [Web code inside desktop apps](https://agentwranglers.se/playbook/desktop-apps/web-code-inside-desktop-apps.md)
- Rule: Every app window runs with Node.js access off, context isolation on and the sandbox on. The page reaches the system only through a short list of named functions, and loads only code packaged with the app.
- Check: A test reads every window's settings and fails on `nodeIntegration: true`, `contextIsolation: false`, `sandbox: false` or `webSecurity: false`. Typing `require` and `process` in a window's developer console returns undefined. No window loads an `http:` or outside `https:` address.
- Risk: An account or system taken over
- How: In a desktop app, a cross-site scripting hole is no longer limited to one page. With Node.js in the window, injected script can read files and run programs as the user. Electron turns Node.js off by default since version 5, context isolation on since 12 and the sandbox on since 20. Never turn them back on. Expose single-purpose functions through `contextBridge`, never `ipcRenderer` itself. In Tauri, grant each window only the commands it needs in its capability file. Load pages from the package or a custom protocol, never remote sites. Set a strict content security policy, as [allow only the scripts you wrote](https://agentwranglers.se/playbook/website/security/content-security-policy.md) says.

## Examples

**Using these examples:** they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

### JavaScript example

```js
// Electron main process: the window gets three named functions and nothing else
const win = new BrowserWindow({
  webPreferences: { preload: path.join(__dirname, 'preload.js'), contextIsolation: true, sandbox: true, nodeIntegration: false },
});
win.loadFile('dist/index.html');

// preload.js
contextBridge.exposeInMainWorld('ledger', {
  openInvoice: id => ipcRenderer.invoke('invoice:open', String(id)),
  exportCsv: month => ipcRenderer.invoke('invoice:export', String(month)),
  version: () => ipcRenderer.invoke('app:version'),
});
```

### Plain text example

```rust
// Tauri: only commands listed here, and allowed in the window's capability file, can be called
#[tauri::command]
fn open_invoice(id: String) -> Result<Invoice, String> {
    invoices::find(&id).map_err(|_| "not found".into())
}

fn main() {
    tauri::Builder::default()
        .invoke_handler(tauri::generate_handler![open_invoice])
        .run(tauri::generate_context!())
        .expect("failed to start");
}
```

## Sources

- [Electron security checklist](https://www.electronjs.org/docs/latest/tutorial/security)

## Related rules

- WEB-141 [Allow only the scripts you wrote](https://agentwranglers.se/playbook/website/security/content-security-policy.md) in Website

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/desktop-apps/web-code-inside-desktop-apps/isolate-web-content">Agent Wranglers desktop apps, extensions and CLIs playbook</a>`. In code you write, add a comment next to it with the same link.

- Next: [Check the sender and content of every message to the main process](https://agentwranglers.se/playbook/desktop-apps/web-code-inside-desktop-apps/validate-ipc.md)
- [Web code inside desktop apps](https://agentwranglers.se/playbook/desktop-apps/web-code-inside-desktop-apps.md)