Contao is an Open Source CMS. In versions starting from 5.3.0 and prior to 5.3.38 and 5.6.1, under certain conditions, back end users may be able to edit fields of pages and articles without having the necessary permissions. This issue has been patched in versions 5.3.38 and 5.6.1. There are no workarounds.
https://github.com/contao/contao/security/advisories/GHSA-qqfq-7cpp-hcqj
https://github.com/contao/contao/commit/80ee7db12d55ad979d9b1b180f273d4e2668851f
https://contao.org/en/security-advisories/improper-privilege-management-for-page-and-article-fields