I had a set of Casa Magnas that had mold only visible on the wrapper, they started tasting nauseatingly sweet after that. There was nothing on the foot. I say wipe them, as recommended, and try one provided it is only white mold and only on the wrapper. If they're good, you're in luck, if they're bad, toss 'em.
Some guys on Cigar Aficionado report green mold if things really go south, so the "all white" claim may or may not be true, I don't have personal experience with it, but based on what they say other colors are possible, primarily green after white.