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. The cloud API had a hidden parameter, which allowed an authenticated user to reconfigure the server URL for a device registered to their account. In combination with an insecure device registration vulnerability, this allowed an attacker to reconfigure a maliciously registered device to their own rogue replica of the myStrom API and issue commands to the device, including firmware update commands.

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.

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. The process of registering a device with a cloud account was based on an activation code derived from the device MAC address. By guessing valid MAC addresses or using MAC addresses printed on devices in shops and reverse engineering the protocol, an attacker would have been able to register previously unregistered devices to their account. When the rightful owner would have connected them after purchase to their WiFi network, the devices would not have registered with their account, would subsequently not have been controllable from the owner's mobile app, and would not have been visible in the owner's account. Instead, they would have been under control of the attacker.

myStrom WiFi Switch V1 devices before 2.66 did not sanitize a parameter received from the cloud that was used in an OS command. Malicious servers were able to run operating system commands on the device.

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. The SSL/TLS server certificate in the device to cloud communication was not verified by the device. As a result, an attacker in control of the network traffic of a device could have taken control of a device by intercepting and modifying commands issued from the server to the device in a Man-in-the-Middle attack. This included the ability to inject firmware update commands into the communication and cause the device to install maliciously modified firmware.