The Grey Opaque theme for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘url’ parameter within the theme's Download-Button shortcode in all versions up to, and including, 2.0.1 due to insufficient input sanitization and output escaping. 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 an injected page.