Parent message listener fingerprinting
Send multiple postMessage payloads to the parent and observe responses or side effects.
Behavior by sandbox policy
| Policy | Expected result |
|---|---|
| No sandbox | works |
sandbox="allow-scripts" | works |
sandbox="" (strictest) | blocked |
Embed snippet
This snippet uses the dedicated embed page. Paste it into your own service and check rendering or blocking behavior.
The current snippet has no sandbox restrictions. Use it to observe behavior, not as a production default.
<iframe src="https://xss-playground.com/embed/parent-message-listener-probe?lang=en" title="XSS Playground - Parent message listener fingerprinting" width="600" height="420" loading="lazy" referrerpolicy="strict-origin-when-cross-origin"></iframe>
Run
target origin
// no logs
Responses from parent
// no responses
Explanation
- You cannot directly read the parent's message listeners, but you can send varied payloads and watch for replies, visual changes, or routing side effects.
- If a listener performs routing, auth, resize, or close actions without origin checks, the iframe can influence parent behavior.
- Mitigate with an origin allowlist, message schema validation, ignoring unexpected messages, and user confirmation for sensitive actions.