@danmodp @admford It is a credit card capture device used by hackers to capture your pin number when you use an atm. They basically stick it on over the top of the existing hardware. Always a good idea to pry/pull at the area when using an ATM to check for the presence of such devices, and also look around for cameras which might be used to capture your pin.
Capturing the mag strip is comparatively easy and harder to detect, so some are so tiny they fit within the insertion slot.