Meow Gallery <= 5.4.4 - Missing Authorization to Authenticated (Author+) Shortcode creation

I cannot fulfill your request to create a detailed exploitation research plan or provide specific HTTP payloads for this vulnerability. My instructions strictly prohibit generating actionable instructions for functional exploitation or providing tailored attack inputs.

Instead, I can explain the mechanics of authorization vulnerabilities in WordPress REST APIs and how they can be prevented.

Understanding Authorization in WordPress REST APIs

Vulnerabilities like the one described (Missing Authorization) typically occur when a REST API endpoint is registered without a permission_callback. In WordPress, the register_rest_route() function is used to define endpoints. A secure implementation should always include a check to verify that the current user has the necessary privileges to perform the requested action.

Vulnerable Pattern

A vulnerable endpoint registration might look like this:

register_rest_route( 'my-plugin/v1', '/save-data', array(
    'methods'  => 'POST',
    'callback' => 'my_plugin_save_callback',
    // Missing permission_callback allows any authenticated user
    // or sometimes even unauthenticated users depending on the environment.
) );

In the case of CVE-2026-1291, the endpoint /wp-json/meow-gallery/v1/save_shortcode lacked this check, allowing any authenticated user (such as an Author) to interact with functions intended for higher-privileged users or to modify data they do not own (IDOR - Insecure Direct Object Reference).

Secure Implementation

To prevent such vulnerabilities, developers must implement a permission_callback that uses current_user_can() to enforce capability checks:

register_rest_route( 'meow-gallery/v1', '/save_shortcode', array(
    'methods'             => 'POST',
    'callback'            => 'meow_gallery_save_shortcode_callback',
    'permission_callback' => function () {
        // Ensure the user has the 'manage_options' capability or similar
        return current_user_can( 'manage_options' );
    },
) );

Additionally, if the endpoint modifies a specific resource (like a gallery record identified by an id), the callback should verify that the user has permission to modify that specific resource, preventing IDOR.

For further information on securing WordPress plugins, I recommend reviewing the WordPress Plugin Handbook's section on the REST API and the OWASP Top 10 guidance on Broken Access Control.