Responsive Thumbnail Slider < 1.1.53 - Reflected Cross-Site Scripting via 'id' Parameter

The Wp Responsive Thumbnail Slider plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'id' parameter in versions up to, and excluding, 1.1.53. This is due to insufficient input sanitization and output escaping in the responsive_thumbnail_image_management() function, which echoes $_GET['id'] directly into a double-quoted HTML attribute with no esc_attr() call. The only guard is a loose PHP numeric comparison ($_GET['id']>0) that a string beginning with a numeric prefix trivially satisfies, and the addslashes() applied by wp_magic_quotes() is inert in HTML-attribute context because backslash is not an HTML escape character. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a specially crafted link.