The small hybrid cameras with interchangeable lenses from Sony, the Sony A7 and A7r know quite a (expected) success but the manufactured just recognized a fairly big fail: a A light leakage is possible between the body and the lens at the lens attachement. Not good…. The lens mount lets some light leak into the camera with all the associated bad consequences. Right now, it is impossible to tell how many cameras are involved, but it does not appear to be marginal cases only.
Sony does not go into great details, but says that they are working on a correction for the issue (I would not like to be one of the engineers tasked with this). In the mean time, the owners would better be using soemthing to mask this part of the camera: gaffer tape, a large elastic rubber band, or elastic hair ties (as shown on BTC).