Apple in iOS 12.4 mistakenly unpatched a vulnerability that was fixed in the iOS 12.3 update, leading to a new jailbreak available for iOS 12.4 devices, reports Motherboard.
Hackers discovered the vulnerability over the weekend and Pwn20wnd created a publicly available, free jailbreak that works on devices running the latest version of iOS or any version of iOS below iOS 12.3.
Most jailbreak code is kept private to keep Apple from patching it, so this is the first time that a public jailbreak has been available in a while. It was apparently discovered when a user tested an older jailbreak on iOS 12.4 and found the patch had been reverted.
Security researcher Jonathan Levin told Motherboard that the accidental vulnerability also once again makes iPhone users vulnerable to a "100+ day exploit," referring to how long the bug has been around.
Ned Williamson from Google Project Zero said that the bug could be exploited to install spyware on a target iPhone.
The researcher told Motherboard that "somebody could make a perfect spyware" taking advantage of Apple's mistake. For example, he said, a malicious app could include an exploit for this bug that allows it to escape the usual iOS sandbox--a mechanism that prevents apps from reaching data of other apps or the system--and steal user data.
Another scenario is a hacker including the exploit in a malicious webpage, and pairing it with a browser exploit, according to the researcher.
A third security researcher, Stefan Esser said that people should be careful what apps they download from the App Store right now. "Any such app could have a copy of the jailbreak in it," he wrote on Twitter.
Multiple users have confirmed that the jailbreak works and that their devices have been jailbroken using the new software. Apple has not commented on how or why the vulnerability was unpatched, but the company will likely have a fix available soon.
