Admidio versions before 5.0.11 have an insecure direct object reference vulnerability in the save_temporary mode of mylist_function.php. Authenticated users can exploit this flaw to hijack list configurations by enumerating global list UUIDs and overwriting admin-curated global lists or other users' private lists. This allows attackers to transfer ownership and demote global lists to personal configurations. The vulnerability has a CVSS 3.1 score of 4.3, indicating medium severity.