The WP Subtitle WordPress plugin before 3.4.1 adds a subtitle field and provides a shortcode to display it via wp_subtitle. The subtitle is stored as a custom post meta with the key: \wps_subtitle\ which is sanitized upon post save/update however is not sanitized when updating it directly from the post meta update button (via AJAX) - and this makes the XSS exploitable by authenticated users with a role as low as contributor.