After providing developers with beta build 13F14 of the upcoming OS X Mavericks 10.9.5 last week, Apple today has released yet another build of the beta.

Build 13F18 is available now and asks developers to focus on USB, USB Smart Cards, Safari, Graphics, Thunderbolt and Gatekeeper integration with 10.9.5. Apple also reminded developers and testers of recent app signing changes for Gatekeeper: Signatures created with OS X version 10.8.5 or earlier (“v1 signatures”) are obsoleted and will no longer be recognized by Gatekeeper. 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”).

As always, the update is available to those running the previous seed through an update in the Mac App Store. The update is also available to testers in Apple’s AppleSeed program.