The Bookero.pl – system rezerwacji online plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the bookero_products shortcode's hide_products (and filter_products) attributes in versions up to and including 2.2. This is due to insufficient input sanitization and output escaping in the bookero_products() function — the raw attribute value is concatenated directly into an inline <script> block without any escaping. This makes it possible for authenticated attackers with contributor-level access and above to inject arbitrary web scripts into pages that will execute whenever a user accesses the injected page.