Contao 4.8.4 and 4.8.5 has Improper Encoding or Escaping of Output. It is possible to inject insert tags into the login module which will be replaced when the page is rendered.
https://github.com/advisories/GHSA-jc43-qrrp-98f5
https://euvd.enisa.europa.eu/vulnerability/EUVD-2019-0796
https://contao.org/en/security-advisories/insert-tag-injection-in-the-login-module.html