PDF for WPForms <= 6.3.0 - Missing Authorization

This research plan targets CVE-2025-68534, a missing authorization vulnerability in the PDF for WPForms plugin (<= 6.3.0). The vulnerability allows Subscriber-level users to perform unauthorized actions, likely modifying plugin settings or PDF templates, because the plugin fails to perform a current_user_can() check in an AJAX handler.

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1. Vulnerability Summary

• Vulnerability: Missing Authorization (Insecure Direct Object Reference / Privilege Escalation to Action).
• Location: An AJAX handler function registered via wp_ajax_ in the plugin's admin or AJAX controller.
• Cause: The function verifies a nonce (CSRF protection) but lacks a capability check (e.g., current_user_can('manage_options')), allowing any authenticated user (including Subscribers) to trigger the logic.
• Impact: Unauthorized modification of plugin configuration, PDF templates, or font settings.

2. Attack Vector Analysis

• Endpoint: wp-admin/admin-ajax.php
• Action (Inferred): Likely related to the Drag and Drop builder or settings. Potential candidates: pdf_for_wpforms_save_settings, pdf_wpforms_update_template, or pdf_wpforms_save_font.
• Authentication: Authenticated (Subscriber+).
• Payload: Sent via POST to admin-ajax.php.
• Required Parameters:
  • action: The vulnerable AJAX action string.
  • _wpnonce or a custom nonce parameter (e.g., security, nonce).
  • Data parameters (e.g., settings[], template_id, css).

3. Code Flow (Trace Path)

1. Entry Point: The plugin registers an AJAX action using add_action( 'wp_ajax_<action_name>', ... ).
2. Hook: WordPress core triggers the callback function when a logged-in user hits admin-ajax.php with the matching action.
3. Verification (Insufficient): The callback function likely calls check_ajax_referer( 'action_string', 'parameter_name' ) or wp_verify_nonce().
4. Authorization (Missing): The function proceeds to update database options (e.g., update_option()) or post meta without checking current_user_can().
5. Sink: Modification of plugin state or templates.

4. Nonce Acquisition Strategy

To exploit this as a Subscriber, we must find where the plugin exposes the nonce to authenticated users.

1. Identify Script Localization: The nonce is likely localized in the WordPress admin dashboard.
2. Test Page: Even if the plugin doesn't have a dedicated Subscriber menu, it may enqueue its admin scripts globally or on the profile.php page.
3. Detection Script:
   • Login as a Subscriber.
   • Navigate to wp-admin/profile.php.
   • Use browser_eval to search for localized objects.
   • Inferred JS Object: pdf_wpforms_admin or wpforms_pdf_builder.
   • Inferred Key: nonce or security.

Action Plan for Agent:

// Example browser_eval to find the nonce
JSON.stringify(Object.keys(window).filter(key => key.toLowerCase().includes('pdf') || key.toLowerCase().includes('wpforms')));
// Then drill down:
window.pdf_wpforms_admin?.nonce;

5. Exploitation Strategy

Step 1: Discover the Action and Nonce Key

Search the plugin source for AJAX registrations:

grep -rn "wp_ajax_" wp-content/plugins/pdf-for-wpforms/

Identify the callback function and check for current_user_can.

Step 2: Identify Nonce Action and Variable

Locate wp_create_nonce or check_ajax_referer in the identified function. Note the action string used (e.g., pdf-for-wpforms-admin). Search for where this nonce is passed to the frontend:

grep -rn "wp_localize_script" wp-content/plugins/pdf-for-wpforms/

Step 3: Extract Nonce as Subscriber

1. Create a Subscriber user via WP-CLI.
2. Use the browser_navigate tool to log in as the Subscriber.
3. Navigate to wp-admin/index.php.
4. Execute browser_eval to extract the nonce from the localized JS variable identified in Step 2.

Step 4: Execute Unauthorized Action

Using the http_request tool, send a POST request to admin-ajax.php.

Example Payload (Inferred):

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

  action=pdf_for_wpforms_save_settings&security=[EXTRACTED_NONCE]&pdf_settings[test_mode]=1&pdf_settings[unauthorized_access]=pwned
  

6. Test Data Setup

1. Install Plugin: Ensure pdf-for-wpforms version 6.3.0 is installed.
2. Create User: wp user create attacker attacker@example.com --role=subscriber --user_pass=password
3. Configure Plugin: Ensure the plugin is active and has at least one default setting or template existing.

7. Expected Results

• HTTP Response: A 200 OK or {"success":true} response.
• System State: The plugin settings or a specific PDF template is modified in the wp_options table or wp_postmeta table.

8. Verification Steps

After the http_request, verify the change via WP-CLI:

# If it modifies options:
wp option get pdf_for_wpforms_settings

# If it modifies template metadata:
wp post list --post_type=pdf_template --fields=ID,post_title
wp post meta list [ID]

9. Alternative Approaches

• Action Discrepancy: If wp_ajax_ is not found, check for admin_init hooks that handle $_POST or $_GET directly without capability checks.
• Generic Nonce: Check if the plugin uses wp_create_nonce( -1 ) or a very common action string like wpforms-admin.
• REST API: Check if the plugin registers any REST routes via register_rest_route without a permission_callback.

  grep -rn "register_rest_route" wp-content/plugins/pdf-for-wpforms/