Jailbreaking iOS devices is like playing a game of whack-a-mole with Apple. This is because for every exploit that jailbreakers use to jailbreak iOS devices, Apple will eventually patch it, leading to that particular jailbreak become redundant. This could also be why over the years, jailbreaking has become a lot less popular than ever due to the hassle involved.
However, it seems that in a tweet by axi0mX, it appears that a new iPhone exploit has been discovered that could potentially lead to a “permanent” jailbreak, one that Apple might not necessarily be able to patch, at least not anytime soon. This is because the exploit involved is a bootrom exploit, which takes advantage of the code in iOS that loads whenever the device is booted up.
This means that Apple will not be able to patch it using software, and it is also possibly the first bootrom-level exploit released since the iPhone 4. However, this only seems to affect devices running the A5 chipset (iPhone 4S) to the A11 chipset (iPhone X) because apparently Apple did fix the vulnerability in the A12 chipset, so newer iPhones won’t be able to take advantage of it.
Before you get too excited, note that there is no jailbreak available at the moment, and if and when it does become available, it is a tethered jailbreak meaning that it can only be done over USB which does limit its usefulness.