A vulnerability has been identified in SIEMENS LOGO!8 (6ED1052-xyyxx-0BA8 FS:01 to FS:06 / Firmware version V1.80.xx and V1.81.xx), SIEMENS LOGO!8 (6ED1052-xyy08-0BA0 FS:01 / Firmware version < V1.82.02). The integrated webserver does not invalidate the Session ID upon user logout. An attacker that successfully extracted a valid Session ID is able to use it even after the user logs out. The security vulnerability could be exploited by an attacker in a privileged network position who is able to read the communication between the affected device and the user or by an attacker who is able to obtain valid Session IDs through other means. The user must invoke a session to the affected device. At the time of advisory publication no public exploitation of this security vulnerability was known.