WordPress Plugin: wp-subtitle: CVE-2022-1393: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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.