Lorenzo Franceschi-Bicchierai, writing for Motherboard:
Someone just posted what experts say is the source code for a core component of the iPhone’s operating system on GitHub, which could pave the way for hackers and security researchers to find vulnerabilities in iOS and make iPhone jailbreaks easier to achieve.
The GitHub code is labeled “iBoot,” which is the part of iOS that is responsible for ensuring a trusted boot of the operating system. In other words, it’s the program that loads iOS, the very first process that runs when you turn on your iPhone. It loads and verifies the kernel is properly signed by Apple and then executes it—it’s like the iPhone’s BIOS.
The code says it’s for iOS 9, an older version of the operating system, but portions of it are likely to still be used in iOS 11.
Apple has already filed a copyright takedown request with GitHub, which resulted in the code being removed, but that won’t help much — the code is out in the wild.