Exploitation Research Plan: CVE-2025-4202 (Multicollab Missing Authorization)

1. Vulnerability Summary

The Multicollab: Content Team Collaboration and Editorial Workflow plugin for WordPress is vulnerable to Missing Authorization in the cf_add_comment function (likely an AJAX handler) in versions up to and including 5.2. This vulnerability allows an authenticated attacker with Subscriber-level permissions to add comments to arbitrary collaborations on any post, regardless of whether they have permission to edit or comment on that specific content.

2. Attack Vector Analysis

• Endpoint: /wp-admin/admin-ajax.php
• Action: cf_add_comment
• HTTP Method: POST
• Authentication: Required (Subscriber level or higher)
• Vulnerable Parameter: post_id (allowing comments on arbitrary posts)
• Preconditions:
  • The plugin must be active.
  • A Subscriber account must be available.
  • A target Post (e.g., published by an Admin) must exist.

3. Code Flow (Inferred)

1. The plugin registers an AJAX action for cf_add_comment using add_action( 'wp_ajax_cf_add_comment', ... ).
2. The JS file admin/assets/js/commenting-block-admin.js interacts with the commenting system, utilizing currentUserData and checking capabilities via the mdstore (Gutenberg data store).
3. When the AJAX request is sent, the PHP function cf_add_comment is invoked.
4. The function likely retrieves post_id and comment_content from the $_POST superglobal.
5. Critical Flaw: The function fails to perform a capability check (e.g., current_user_can( 'edit_post', $post_id )) before inserting the comment into the database (likely the wp_multicollab_comments table or the standard wp_comments table with custom meta).

4. Nonce Acquisition Strategy

The plugin localizes data for its JS scripts. Based on the presence of currentUserData in admin/assets/js/commenting-block-admin-functions.js, the nonce is likely stored in a related global object.

1. Identify the Localization Object: The plugin likely uses multicollab_vars, mc_vars, or cf_vars.
2. Trigger Script Loading: Multicollab scripts typically load on the post editor page or pages where collaboration is enabled.
3. Procedure:
   • Create a test page as Admin.
   • Access the page as a Subscriber.
   • Use browser_eval to find the nonce:
     • browser_eval("window.mc_vars?.nonce")
     • browser_eval("window.multicollab_vars?.nonce")
     • browser_eval("window.currentUserData?.nonce") (inferred)
4. Bypass Check: If wp_verify_nonce is called with action -1 or if the check is missing entirely, the exploit may proceed without a specific action-bound nonce.

5. Exploitation Strategy

Step 1: Authentication

Authenticate as a Subscriber user and maintain the session cookies.

Step 2: Identify Target

Select a Target Post ID (post_id) created by an Administrator that the Subscriber should not be able to comment on.

Step 3: Send Malicious AJAX Request

Construct a POST request to admin-ajax.php.

Request Details:

• URL: http://localhost:8080/wp-admin/admin-ajax.php
• Method: POST
• Headers:
  • Content-Type: application/x-www-form-urlencoded
  • Cookie: [Subscriber_Session_Cookies]
• Body:

  action=cf_add_comment&post_id=[TARGET_POST_ID]&comment_content=Unauthorized+Collaboration+Comment&nonce=[NONCE]&is_suggestion=0&board_id=el_target_123
  

  (Note: board_id and is_suggestion are inferred common parameters for Multicollab comments based on the JS source's use of getBoardIds).

6. Test Data Setup

1. Users:
   • Create an Admin user (admin_user).
   • Create a Subscriber user (attacker_subscriber).
2. Content:
   • As admin_user, create a private post or a published post (ID 123).
   • Enable Multicollab collaboration on this post if the plugin settings require it.
3. Plugin Configuration: Ensure the plugin is active and "Commenting" is enabled in Multicollab settings.

7. Expected Results

• The server should respond with a 200 OK and a JSON response indicating success (e.g., {"success":true,"data":...}).
• The comment should be visible in the Multicollab collaboration sidebar when viewing the post as an Administrator.

8. Verification Steps

1. Database Check: Query the wp_multicollab_comments table (if present) or wp_comments for the injected content:
   • wp db query "SELECT * FROM wp_multicollab_comments WHERE comment_content LIKE '%Unauthorized%';" --path=/var/www/html
2. CLI Verification:
   • wp comment list --post_id=[TARGET_POST_ID]
3. UI Verification: Navigate to the Post Edit screen for the target post as Admin and check the collaboration panel for the Subscriber's comment.

9. Alternative Approaches

• Missing Parameters: If cf_add_comment fails, try mc_add_comment (alternative naming convention observed in some versions).
• Suggestion Vector: Try setting is_suggestion=1 and providing suggestion_data to see if unauthorized suggestions can also be injected via the same missing check.
• Nonce Bypass: If a valid nonce cannot be found, try the request without the nonce parameter to see if the plugin fails to verify it entirely.