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.
The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.