By limiting access to sensitive resources on a per-app basis, App Sandbox provides a last line of defense against the theft, corruption, or deletion of user data, or the hijacking of system hardware, if an attacker successfully exploits security holes in your app. For example, a sandboxed app must explicitly state its intent to use any of the following resources using entitlements:
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On the other hand, a sandboxed app has access to the specific resources you request, allows users to expand the sandbox by performing typical actions in the usual way (such as drag and drop), and can automatically perform many additional actions deemed safe ...