The Download Manager plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'sid' parameter of the 'wpdm_members' shortcode in versions up to and including 3.3.52. This is due to insufficient input sanitization and output escaping on the user-supplied 'sid' shortcode attribute. The sid parameter is extracted without sanitization in the members() function and stored via update_post_meta(), then echoed directly into an HTML id attribute in the members.php template without applying esc_attr(). This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses the injected page.