  By analysing the short-cadence K2 photometry from the observing Campaign 12
we refine the system parameters of hot Jupiter WASP-28b and hot Saturn
WASP-151b. We report the non-detection and corresponding upper limits for
transit-timing and transit-duration variations, starspots, rotational and
phase-curve modulations and additional transiting planets. We discuss the cause
of several background brightening events detected simultaneously in both
planetary systems and conclude that they are likely associated with the passage
of Mars across the field of view.
