Shopware before 5.5.8 has XSS via the Query String to the backend/Login or backend/Login/load/ URI.
https://www.shopware.com/en/changelog/#5-5-8
https://www.netsparker.com/web-applications-advisories/ns-19-004-cross-site-scripting-in-shopware/
http://seclists.org/fulldisclosure/2019/Jun/32
http://packetstormsecurity.com/files/153145/Shopware-5.5.6-Cross-Site-Scripting.html