An issue was discovered in myStrom WiFi Switch V1 before 2.66, WiFi Switch V2 before 3.80, WiFi Switch EU before 3.80, WiFi Bulb before 2.58, WiFi LED Strip before 3.80, WiFi Button before 2.73, and WiFi Button Plus before 2.73. Devices did not authenticate themselves to the cloud in device to cloud communication. This lack of device authentication allowed an attacker to impersonate any device by guessing or learning their MAC address.