an accidental exposure

I am experimenting by uploading a shot that was taken by mistake. Having checked the previous shots on the camera's screen, I was about to shut the camera down to remove the card to put the images on my PC, when I must have pressed the wrong button.
For those too young to remember the expression, an exposure was what taking a photo on film was called. It originated when old plate cameras were in use and the light excluding cover of the plate was removed and then the lens cap. The plate, with its photo-sensitive chemicals on it was thus 'exposed' to the light from the subject. I suppose the principle is still the same as the shutter opens and light goes onto the light-sensitive cells.