The WS Form LITE – Drag & Drop Contact Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'field_<id>[0][0]' parameter in all versions up to, and including, 1.12.18 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This is possible because the client-side esc_html() helper returns any non-string value unchanged, allowing a nested-array payload coerced via Array.prototype.toString to reach jQuery .append() unescaped.