Multiple cross-site scripting (XSS) vulnerabilities in the Ninja Forms plugin before 2.8.9 for WordPress allow (1) remote attackers to inject arbitrary web script or HTML via the ninja_forms_field_1 parameter in a ninja_forms_ajax_submit action to wp-admin/admin-ajax.php or (2) remote administrators to inject arbitrary web script or HTML via the fields[1] parameter to wp-admin/post.php.