Update the WordPress SEO Plugin by Squirrly SEO plugin to the latest available version (at least 12.1.21).
Rafie Muhammad (Patchstack) discovered and reported this Cross Site Scripting (XSS) vulnerability in WordPress SEO Plugin by Squirrly SEO 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 been fixed in version 12.1.21.