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.
https://github.com/Quadron-Research-Lab/CVE/blob/main/CVE-2021-3111.pdf
https://documentation.concrete5.org/developers/introduction/version-history/855-release-notes
https://documentation.concrete5.org/developers/introduction/version-history
http://packetstormsecurity.com/files/161997/Concrete5-8.5.4-Cross-Site-Scripting.html
http://packetstormsecurity.com/files/161600/Concrete5-8.5.4-Cross-Site-Scripting.html