TYPO3 Core

The fetchGroupData() function within the \TYPO3\CMS\Core\Authentication\BackendUserAuthentication class sets the value of the groupData property (an array of permissions for various access list groups).

The function processes combined permissions from both user and groups to ensure that there are unique values in each list, such as modules, available_widgets, etc.

However, there seems to be a missing check for unique values in the filemounts group.