Why is this exploit significant? It cannot be addressed with a software update, only a hardware revision can address this. Named “checkm8,” the exploit is a bootrom vulnerability (initial code that iOS devices load when they boot up) that gives hackers access to iOS devices on a level that Apple cannot block. The iOS hacker claims the exploit is permanent and can be used to create a jailbreak on all iOS devices ranging from iPhone 4s (A5 chip) to iPhone 8 and iPhone X (A11 chip). The exploit does not impact the latest two chipsets, A12 and A13.
When reading further, the jailbreak itself is not there yet, a lot of fear theory around what it could do. The article goes on to state that jailbreakers deem this to be a tethered exploit, meaning it can only be used/activated via USB and a computer. It could be a game-changer If this exploit tool leads to an untethered jailbreak which could then be applied to hundreds of missions of iOS devices.
https://thehackernews.com/2019/09/bootrom-jailbreak-ios-exploit.html