Despite the potential seriousness of this problem, it is important to note a couple of things. The first is that actually exploiting those fraudulent certificates requires of things to go just right for the would-be attackers—they'd have to create perfect replicas of the Websites in question convince users to visit them. It’s also worth pointing out that the above solution only pertains to Safari. Other popular Mac browsers, like Chrome or Firefox, rely on a different certificate validation mechanism, but they ought to be safe as long as you keep them up-to-date.