---
title: "Accept push endpoints only from known push · Agent Wranglers"
url: https://agentwranglers.se/playbook/notifications/push-notifications/push-endpoint-allow-list
updated: 2026-10-21
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Accept push endpoints only from known push services

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Push notifications](https://agentwranglers.se/playbook/notifications/push-notifications.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers). Updated 2026-10-21.

- Level: Required
- Chapter: [Push notifications](https://agentwranglers.se/playbook/notifications/push-notifications)
- Rule: Before you store a web push subscription, check that its endpoint is HTTPS on a push service host you allow. Refuse every other address.
- Risk: An account or system taken over
- How: The browser sends the endpoint, so an attacker can send any address and make your server POST to it later. Keep an allow list of the push services your supported browsers use, such as `fcm.googleapis.com`, `updates.push.services.mozilla.com` and `*.push.apple.com`. Apple names `*.push.apple.com` as the hosts a sending server must reach. Refuse any other host, any port, and any `http:` address, and do not follow redirects when you send. This is the push form of [Fetch only allowed addresses](https://agentwranglers.se/playbook/adversarial-testing/requests-and-files/block-server-side-request-forgery).
- Check: An API test posts subscriptions with the endpoints `https://169.254.169.254/latest`, `http://fcm.googleapis.com/fcm/send/x` and `https://push.example.com/x`. Each one gets 422, and no row is stored.

## 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
const PUSH_HOSTS = ['fcm.googleapis.com', 'updates.push.services.mozilla.com'];
const PUSH_HOST_SUFFIXES = ['.push.apple.com', '.notify.windows.com'];

export function isPushEndpoint(endpoint) {
  let url;
  try { url = new URL(endpoint); } catch { return false; }
  if (url.protocol !== 'https:' || url.port !== '') return false;
  return PUSH_HOSTS.includes(url.hostname) || PUSH_HOST_SUFFIXES.some(suffix => url.hostname.endsWith(suffix));
}
```

### Python example

```python
from urllib.parse import urlsplit

PUSH_HOSTS = {"fcm.googleapis.com", "updates.push.services.mozilla.com"}
PUSH_HOST_SUFFIXES = (".push.apple.com", ".notify.windows.com")

def is_push_endpoint(endpoint: str) -> bool:
    url = urlsplit(endpoint)
    if url.scheme != "https" or url.port is not None or not url.hostname:
        return False
    return url.hostname in PUSH_HOSTS or url.hostname.endswith(PUSH_HOST_SUFFIXES)
```

## Sources

- [OWASP Server-Side Request Forgery Prevention Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Server_Side_Request_Forgery_Prevention_Cheat_Sheet.html)
- [Apple, Sending web push notifications in web apps and browsers](https://developer.apple.com/documentation/usernotifications/sending-web-push-notifications-in-web-apps-and-browsers)

## Related rules

- [Fetch only allowed addresses](https://agentwranglers.se/playbook/adversarial-testing/requests-and-files/block-server-side-request-forgery) in Security testing

**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/notifications/push-notifications/push-endpoint-allow-list">Agent Wranglers notifications playbook</a>`. In code you write, add a comment next to it with the same link.

- Previous: [Unlink push from the account at sign-out](https://agentwranglers.se/playbook/notifications/push-notifications/unlink-push-on-sign-out)
- Next: [Send personal messages only to the person's devices](https://agentwranglers.se/playbook/notifications/push-notifications/personal-push-to-devices)
- [Push notifications](https://agentwranglers.se/playbook/notifications/push-notifications)