The Express Entries Dashboard in Concrete5 8.5.4 allows stored XSS via the name field of a new data object at an index.php/dashboard/express/entries/view/ URI.
packetstormsecurity.com/files/161600/Concrete5-8.5.4-Cross-Site-Scripting.html
packetstormsecurity.com/files/161997/Concrete5-8.5.4-Cross-Site-Scripting.html
documentation.concrete5.org/developers/introduction/version-history
documentation.concrete5.org/developers/introduction/version-history/855-release-notes
github.com/Quadron-Research-Lab/CVE/blob/main/CVE-2021-3111.pdf