The Passeum Ticketing plugin for WordPress is vulnerable to Stored Cross-Site Scripting in all versions up to, and including, 1.0. This is due to the `get_shop_url()` method returning the `shop_name` setting value without sanitization when it begins with "http", combined with insufficient validation in the `validate_shop_name()` function which only checks for empty values and string type. This makes it possible for authenticated attackers, with Administrator-level access and above, to inject arbitrary external scripts by setting the `shop_name` to an attacker-controlled URL (e.g., `https://attacker.com`), which causes the plugin to enqueue external JavaScript and CSS from the attacker-controlled domain via `wp_register_script()` and `wp_register_style()`. The injected scripts execute on every frontend page containing any Passeum Ticketing shortcode, affecting all site visitors. Please note that this does not affect single-site installations as administrators already have the `unfiltered_html` capability.