It wasn't that long ago that the OS X Mavericks 10.9.3 update was sent to users, but today Apple seeded the first beta of the 10.9.4 update to developers. There's no word right now what's in OS X 10.9.4, but if we had to guess we'd say it's more bug fixes for Mavericks and possibly some back-end tweaks to help with the coming update and transition to OS X 10.10 Syrah (which we'll be learning more about next week at WWDC 2014).
Source: 9to5Mac
