Apple might have made it harder for other people to gain access to your iPhone.
A feature named "USB Restricted Mode" was spotted in a beta version for iOS 11.4, as noted by ZDNet. USB Restricted Mode keeps USB accessories from connecting to the phone's Lightning port if you haven't unlocked it in the past seven days, according to the beta testers. So if you want to connect a USB accessory to your iPhone, you'll have to keep unlocking it every so often. Charging, however, still reportedly works.
USB Restricted Mode seems to be Apple's response to, a device that claims it can unlock iPhones by guessing at the passcode again and again until it gets it right. In order for GrayKey to work, you need to plug it into the iPhone's Lightning port, but with USB Restricted Mode turned on, it's not clear if GrayKey would be able to connect.
Apple encrypts iPhones so [theoretically] only the device owner can get into them, but law enforcement agencies have often asked Apple to provide them with a backdoor. As ZDNet notes, GrayKey could be a useful tool for law enforcement to break into locked iPhones, but perhaps USB Restricted Mode may prevent that from happening.
Beta testers also noticed the feature in the iOS 11.3 beta, but it was pulled before the general release.
Apple did not immediately respond to a request for comment.