The Shariff Wrapper plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'headline' parameter in the [shariff] shortcode in all versions up to, and including, 4.6.20 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. The vulnerability occurs because the plugin uses a custom wp_kses implementation with permissive allowed HTML tags, and then performs a str_replace operation that injects HTML after sanitization, allowing event handlers to be introduced through the %total placeholder in the style attribute.