TYPO3 Core

In the usergroup settings, under "allowed excludefields" there are exclude fields shown only for the flexform fields in the tt_content (usually just for pi_flexform field).

Exclude fields from flexforms from tables other than tt_content won't be shown there and will thus always be unavailable for regular editors.

You can replicate the actual bug by installing for example extension powermail v1.6.4 and trying to set up access rights for the formfield's mandatory checkbox.

Please review the attached patch and integrate it in the core. It allows setting access rights for all exclude fields in any table's flexform fields.