As outlined in a post to Adobe Secure Software Engineering Team (ASSET) blog, the App Sandbox feature in Mavericks lets Adobe limit the plugin's capabilities to read and write files, as well as what assets Flash Player can access.
Adobe platform security specialist Peleus Uhley explained that in Mavericks, Flash Player calls on a plugin file -- specifically com.macromedia.Flash Player.plugin.sb -- used to define security permissions defined by an OS X App Sandbox. The player's capabilities are then restricted to only those operations that are required to operate normally.
In addition, Flash Player can no longer access local connections to device resources and inter-process communications (IPC) channels. Network privileges are also limited to within OS X App Sandbox parameters, preventing Flash-based malware from communicating with outside servers.
Uhley noted that the company has effectively deployed some method of sandboxing with Google's Chrome, Microsoft's Explorer and Mozilla's Firefox browsers. Apple will now be added to that list as long as users are running Safari in Mavericks.
"Safari users on OS X Mavericks can view Flash Player content while benefiting from these added security protections," Uhley said. "We'd like to thank the Apple security team for working with us to deliver this solution."