“I guess I overflowed some buffer and I’ve corrupted the firmware.”
The “encryption” on these Bluetooth Christmas lights was an AES key sitting in a compiled library that someone else had already pulled out. The app capped colours at 5 bits while the controller happily took 8. Cooke sent effect numbers past the 10 the app uses and the lights died for good. A fixed key and zero input validation means anyone within Bluetooth range can brick your tree.