Yoast SEO <= 21.0 is vulnerable to Cross Site Scripting (XSS) vulnerability

The Yoast SEO plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 21.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with seo manager-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.