updated 02:27 pm EDT, Tue August 19, 2014
Gatekeeper added to testing list
Apple has posted a new beta of OS X 10.9.5 for developers and AppleSeed participants, identified as build 13F18. Testing areas remain largely the same -- including Safari, graphics, Thunderbolt, and USB/USB smart cards -- but with the addition of a significant change to Gatekeeper, Apple's app-signing security feature. "Signatures created with OS X version 10.8.5 or earlier ('v1 signatures') are obsoleted and will no longer be recognized by Gatekeeper," Apple reminds the developer audience. "To ensure your apps will run on updated versions of OS X, they must be signed using the codesign tool on OS X version 10.9 or later ('v2 signatures')."
People with the previous beta installed can update it through the Mac App Store.