Several anti-debunkers have argued that evolutionary explanations of our moral beliefs fail to meet a necessary condition on undermining defeat called modal security. They conclude that evolution, therefore, does not debunk our moral beliefs. This article shows that modal security is false if knowledge is virtuous achievement. New information can undermine a given belief without providing reason to doubt that that belief is sensitive or safe. This leads to a novel conception of undermining defeat, and it shows that successful debunking of moral realism is possible.