Specifically, Apple describes the iOS 12.4.1 update as fixing a kernel vulnerability that allowed apps “to execute arbitraty code with system privileges”. From the looks of it, that’s all the update is about. Apple also acknowledged Pwn20wnd, for his assistance.
Pwn20wnd released the jailbreak for iOS 12.4 not too long after the vulnerability was rediscovered. A number of iPhone users had successfully jailbroken their iPhones using it. One of them was Ned Williamson of Google Project Zero, who confirmed that it worked on his iPhone XR. If you don’t have your iPhone jailbroken, then it’s best to get the update as soon as you can. While the update makes jailbreaking impossible again, it also ensures that your iPhone won’t be affected by malware that makes use of the same security bug. (Source: Apple via Engadget)
