I spend a lot of time to study security update by Apple this week. It looks that core foundation vulnerability bring to my attention. As we know Objective-C is a general-purpose, object-oriented programming language used by Apple for the OS X and iOS operating systems. Retrospectively, vendor has urge developer that a good practices will be prevented memory-related problem. I am concerning about the race condition vulnerability found this time. There are two main kinds of problem that result from incorrect memory management. Freeing or overwriting data that is still in use. Not freeing data that is no longer in use causes memory leaks. This is the way to causes the vulnerability (race condition) happens.
Since there are plenty of vulnerabilities address this time. For more details, please refer to official url for reference.
About the security content of iOS 11.3
About the security content of Xcode 9.3