The Customily Product Personalizer plugin for WordPress is vulnerable to Stored Cross-Site Scripting via user cookies in all versions up to, and including, 1.23.3 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. We unfortunately could not get in touch with the vendor through various means to disclose this issue.