No patched version is available. No reply from the vendor.
Rio Darmawan discovered and reported this Cross Site Scripting (XSS) vulnerability in WordPress itemprop WP for SERP/SEO Rich snippets Plugin. This could allow a malicious actor to inject malicious scripts, such as redirects, advertisements, and other HTML payloads into your website which will be executed when guests visit your site. This vulnerability has not been known to be fixed yet.