Following the release of OS X Yosemite this afternoon, Apple quickly pushed out iTunes 12.0.1. As you know, Yosemite includes a refreshed edition of iTunes marked as version 12, and this is an update for the folks who are using the new software.
Not much is mentioned in the change log in terms of what's new in 12.0.1, but it does note that at least one of the changes has to do with security. And given its release time, and .1 build number, we imagine that it includes other bug fixes as well.