GHSA-g8x9-7mgh-7cvj AVideo's GET-Based CSRF in setPermission.json.php Enables Privilege Escalation via Arbitrary Permission Modification

• Packagist wwbn/avideo: <= 26.0 (no fix yet)

Summary The `plugin/Permissions/setPermission.json.php` endpoint accepts GET parameters for a state-changing operation that modifies user group permissions. The endpoint has no CSRF token validation, and the application explicitly sets `session.cookie_samesite=None` on session cookies. This allows an unauthenticated attacker to craft a page with `` tags that, when visited by an admin, silently grant arbitrary permissions to the attacker's user group — escalating the attacker to near-admin access. Details The root cause is a combination of three issues: 1. `$_REQUEST` used instead of `$_POST` (accepts GET parameters): `plugin/Permissions/setPermission.json.php:14-24`: ```php $intvalList = array('users_groups_id','plugins_id','type','isEnabled'); foreach ($intvalList as $value) { if($_REQUEST[$value]==='true'){ $_REQUEST[$value] = 1; }else{ $_REQUEST[$value] = intval($_REQUEST[$value]); } } $obj = new stdClass(); $obj->id = Permissions::setPermission($_REQUEST['users_groups_id'], $_REQUEST['plugins_id'], $_REQUEST['type'], $_REQUEST['isEnabled']); ``` The only authorization check is `User::isAdmin()` at line 10 — there is no CSRF token validation via `isGlobalTokenValid()`. 2. Session cookies set to `SameSite=None`: `objects/include_config.php:134-141`: ```php if ($isHTTPS) { // SameSite=None is intentional: AVideo supports cross-origin iframe embedding ini_set('session.cookie_samesite', 'None'); ini_set('session.cookie_secure', '1'); } ``` This means the admin's session cookie is sent on cross-origin requests, including those initiated by `` tags on attacker-controlled pages. 3. The codebase's own security model requires CSRF tokens on state-mutating endpoints: The comment at `include_config.php:137-138` states: *"All state-mutating endpoints that are vulnerable to CSRF must instead enforce a short-lived globalToken (verifyToken)."* Other endpoints like `saveSort.json.php` and `pluginImport.json.php` enforce `isGlobalTokenValid()`, but `setPermission.json.php` does not. Execution flow: 1. Attacker hosts a page containing `` 2. Admin visits the page (e.g., via link in forum, email, or embedded content) 3. Browser issues GET request with the admin's `SameSite=None` session cookie 4. `User::isAdmin()` passes because the request carries the admin's session 5. `Permissions::setPermission()` grants PERMISSION_FULLACCESSVIDEOS (type=10) to user group 2 6. Any user in group 2 (including the attacker) now has full video admin access The `users_groups_id` values are small sequential integers (typically 1-3 for default groups) and can be trivially enumerated. PoC Step 1: Attacker creates a page granting multiple permissions to their user group (ID 2): ```html Interesting Video Check out this video! ``` Step 2: Attacker sends the link to an admin (social engineering, forum post, etc.) Step 3: When the admin loads the page, all four `` tags fire simultaneously. Expected response for each request (visible in browser dev tools): ```json {"id":"1"} ``` Step 4: Verify — the attacker (a regular user in group 2) now has full video management, user management, upload, and livestream permissions without being an admin. Impact • Privilege escalation: A low-privileged user can gain near-admin permissions (full video access, user management, upload, livestream) by tricking an admin into loading a single page. • No JavaScript required: The attack uses only `` tags, bypassing Content Security Policy restrictions and working even in contexts where scripts are blocked (email clients, forum BBCode, etc.). • Zero interaction beyond page load: Unlike POST-based CSRF that requires form submission or JavaScript, this fires automatically when the page renders. • Chaining: Multiple permissions can be granted simultaneously by embedding multiple `` tags. An attacker can grant their group all available permission types in a single page load. • Blast radius: All users in the targeted group receive the escalated permissions, not just the attacker. Recommended Fix In `plugin/Permissions/setPermission.json.php`, change `$_REQUEST` to `$_POST` and add CSRF token validation: ```php 'POST method required'))); } if (!isGlobalTokenValid()) { die(json_encode(array('error' => 'Invalid CSRF token'))); } $intvalList = array('users_groups_id','plugins_id','type','isEnabled'); foreach ($intvalList as $value) { if($_POST[$value]==='true'){ $_POST[$value] = 1; }else{ $_POST[$value] = intval($_POST[$value]); } } $obj = new stdClass(); $obj->id = Permissions::setPermission($_POST['users_groups_id'], $_POST['plugins_id'], $_POST['type'], $_POST['isEnabled']); die(json_encode($obj)); ``` The AJAX call in `getPermissionsFromPlugin.html.php:84-92` already uses `type: 'post'` but must also send the `globalToken` parameter in its data payload.