When chocolate candy sits around for too long, it gets a “white” buildup on the exterior. What is this white buildup? Is it safe to eat?
Google is my friend. There are two types - sugar bloom, and fat bloom. They are safe to eat.
Thanks to everyone who helped. 
I believe that it is fat, part of the ingredients of the chocolate, a small fraction of which has migrated from the interior of the chocolate to its surface. Yes, it is perfectly safe to eat. It is not mold or bacteria or anything. The flavor may be very slightly impacted, but it will still taste good. It’s chocolate!
ETA: Darn, ninjaed by the OP himself!
You’re welcome.
The Straight Dope is a great place to get answers in almost no time. It took barely seven minutes for your OP. Aren’t you impressed?