Hi @csant,
others have reported to have similar issues. I don’t think you need to worry about the phone being compromised! What I find weird is that it’s ok again after the reboot, all the other users seem to have this issue constantly. In this other topic, it was recommended to raise a ticket with the Support team, they seem to be working on a solution.
Did you upgrade to 1.6 Cherry?
Or did you by any chance charge your phone while this happened?