The European VAT Compliance Assistant for WooCommerce plugin for WordPress is vulnerable to Stored Cross-Site Scripting via CF-IPCountry Header in all versions up to, and including, 1.36.10 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. The malicious header value is persisted verbatim into order post-meta during a guest checkout, meaning no account or authentication is required to plant the payload.