An oversight in the implementation of USB Restricted Mode in iOS 11.4.1 and the iOS 12 Beta 2 potentially allows malicious actors to override the new security feature intended to prevent unauthorized device access. According to a blog post by Oleg Afonin, a security researcher at Elcomsoft, plugging a device into the Lightning port before USB Restricted Mode is engaged interrupts the countdown timer.
As a quick review, USB Restricted Mode is a new feature that limits an iOS-powered device to only charge via USB if it has not been unlocked in the last hour. After one hour, the USB port cannot be used to communicate with a computer or other device. Similarly, this also affects the ability to use USB accessories on a given device. Apple’s support page on the topic indicates that iOS-powered devices will need to be unlocked in order for USB accessories plugged in to a given device to be recognized.
Starting with iOS 11.4.1, if you use USB accessories with your iPhone, iPad, or iPod touch, or if you connect your device to a Mac or PC, you might need to unlock your device for it to recognize and use the accessory. Your accessory then remains connected, even if your device is subsequently locked.