The SPIP jeux plugin versions prior to 4.1.1 contain a reflected cross-site scripting (XSS) vulnerability in the prepropre pipeline. The plugin incorporates untrusted request parameters into HTML output without proper output encoding, allowing attackers to inject arbitrary script content into pages that render a jeux block. When a victim is induced to visit a crafted URL, the injected content is reflected into the response and executed in the victim's browser context.