The Sticky plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the cvmh-sticky shortcode readmoretext attribute in versions up to and including 2.5.6. This is due to insufficient input sanitization and output escaping in the cvmh_sticky_front_render() function — the readmoretext attribute value is passed through apply_filters() and directly concatenated into the HTML output without any escaping function such as esc_html(). 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 a page containing the injected shortcode.