Apple has seeded Mavericks 10.9.5, build 13F18 to developers, just short of a week after seeding build 13F14 to developers. Apple is asking developers to focus on USB, USB Smart Cards, Graphics, Safari, and Thunderbolt.
![OS_X_Mavericks_Build_ 13F18](http://www.mactrast.com/wp-content/uploads/2014/08/OS_X_Mavericks_Build_-13F18.jpg)
The new beta is available via the Update tab in the Mac App Store, and via download from the Mac Developer Center.