Tinycontrol devices such as tcPDU and LAN Controllers LK3.5, LK3.9 and LK4 have two separate authentication mechanisms - one solely for interface management and one for protecting all other server resources. When the latter is turned off (which is a default setting), an unauthenticated attacker on the local network can obtain usernames and encoded passwords for interface management portal by inspecting the HTTP response of the server when visiting the login page, which contains a JSON file with these details. Both normal and admin users credentials are exposed.
This issue has been fixed in firmware versions: 1.36 (for tcPDU), 1.67 (for LK3.5 - hardware versions: 3.5, 3.6, 3.7 and 3.8), 1.75 (for LK3.9 - hardware version 3.9) and 1.38 (for LK4 - hardware version 4.0).
Enabling "Basic Authentication" option mitigates the risk, because an attacker has to log in first prior to exploitation.