vantage6 Improper Access Control vulnerability

vantage6 is privacy preserving federated learning infrastructure. The endpoint /api/collaboration/{id}/task is used to collect all tasks from a certain collaboration. To get such tasks, a user should have permission to view the collaboration and to view the tasks in it. However, prior to version 4.0.0, it is only checked if the user has permission to view the collaboration. Version 4.0.0 contains a patch. There are no known workarounds.