The technical implementation is called the sandbox, and it's a fundamental part of iOS security. Yes, it is possible to bypass the sandbox, but it would involve

The technical implementation is called the sandbox, and it's a fundamental part of iOS security. Yes, it is possible to bypass the sandbox, but it would involve exploiting security vulnerabilities on the user's device, which Apple offers up to a $25k bounty for. You generally have bigger problems if something escapes the sandbox on your device, though :)