GHSA-pfrr-xvrf-pxjx

### Impact
A community member disclosed an issue where verification signatures for requests sent to Reverb's Pusher-compatible API were not being verified. This API is used in scenarios such as broadcasting a message from a backend service or for obtaining statistical information (such as number of connections) about a given channel.

The verification signature is a hash comprised of different parts of the request signed by the app's secret key. The signature is sent as part of the request and should be regenerated by Reverb. Only when both the signature in the request and the one generated by Reverb match should the request be allowed. This helps to verify the request came from a known source.

> [!NOTE]
> This issue only affects the Pusher-compatible API endpoints and not the WebSocket connections themselves. In order to exploit this vulnerability, the application ID which, should never be exposed, would need to be known by an attacker.

The following endpoints were affected:

```
POST /events
POST /events_batch
GET /connections
GET /channels
GET /channel
GET /channel_users
POST /users_terminate
```

### Patches
The issue was resolved by [#252](https://github.com/laravel/reverb/pull/252) and the patch released in [v1.4.0](https://github.com/laravel/reverb/releases/tag/v1.4.0).

### References
[Generating Pusher authentication signatures](https://pusher.com/docs/channels/library_auth_reference/rest-api/#generating-authentication-signatures)