Apple has fixed numerous security bugs in OS X 10.10.2 (kudos).
But (more Apple Core Rot)— shoveled in new manure: when my dual-display System boots, there is no login dialog—just two blank gray screens! Only by unplugging one display does a login dialog appear. I can then login, then plug the display back in (alternately, turning one display off, logging in, then turning the display back on). I know the system is up even though there is no login dialog, because I can connect to it via file sharing.