Remediation
Add the code below to your theme's function files

add_filter('rest_endpoints', function ($endpoints) {
    if (!is_user_logged_in()) {
        return [];
    }
    return $endpoints;
});

add_filter('rest_authentication_errors', function ($result) {
    if (!is_user_logged_in()) {
        return new WP_Error('rest_disabled', __('The REST API is restricted to logged-in users only.'), array('status' => 403));
    }
    return $result;
});

							

Or Download our plugin disable-rest-api-for-guests.zip