Contao is an Open Source CMS. In versions starting from 5.0.0 and prior to 5.3.38 and 5.6.1, the table access voter in the back end doesn't check if a user is allowed to access the corresponding module. This issue has been patched in versions 5.3.38 and 5.6.1. A workaround involves not relying solely on the voter and additionally to check USER_CAN_ACCESS_MODULE.
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.