@BernardSheppard @mattblaze In a hotel I stayed in a few years back, someone discovered an interesting hack: while you could only select a floor after swiping your card (IIRC and only your own), after someone had selected a floor you could select any additional floor by pushing the button of the already selected floor and the new floor at the same time, thanks to the physical wiring of the card-reader add-on.
Not sure whether you'd count that wiring as "software bug" or "physical security issue" 