A race condition was addressed with additional validation. This issue is fixed in tvOS 11.2, iOS 11.2, macOS High Sierra 10.13.2, Security Update 2017-002 Sierra, and Security Update 2017-005 El Capitan, watchOS 4.2. An application may be able to gain elevated privileges.
https://support.apple.com/en-us/HT208334
https://support.apple.com/en-us/HT208331