Mac Rumors posted a news story that Apple has posted a new support document outlining the security content of iOS 4

One issue addressed in iOS 4 involves the ability of third-party applications to access a user's photo library, indirectly allowing the applications to infer a user's location without explicit authorization via the geolocation information. iOS 4 addresses the issue by modifying the Application Sandbox to prevent direct access to the photo library.

  iOS 4 Addresses Over 60 Security Vulnerabilities