Zanz commented on this one day in chat. Apparently no such bug which allows you to win Malignant Cells should exist, nor should anyone have any as a standalone card. Regardless, the forums is not the place to report hackers, cheaters, etc. After researching this matter thoroughly you should send a report of what occurred to Zanz via e-mail. It's really the only way that such information will see daylight, but even then there's a good chance that the system will deal with the person by itself if it really is an issue.