I had a similar happening today where I received a notification not originating from my installation in a foreign language (føler 2 har det pisse varmt / “Sensor 2 is piss hot”).
At the time I didnt know was happening (security breach?) and shutdown my RPi. The myopenhab-portal doesnt show the particular message in the archives. When at home I will bootup and have a look at the local logs, but based on the above I dont expect to find anything.
Edit: layout