PixelYourSite (Free & Pro) - Unauthenticated Stored XSS via Cookie

The PixelYourSite WordPress plugin before 11.4.3, PixelYourSite Pro WordPress plugin before 12.6.8 do not sanitise and escape a cookie value before printing it into the page output, which, on a site running a full-page cache, allows unauthenticated attackers to store a Cross-Site Scripting payload in the cached page that is then served to other visitors.