Apple has issued a rare iOS 12 update to address a security flaw in older iPhones and iPads.

Owners of the iPhone 5s and iPhone 6 should update to iOS 12.5.6 as soon as possible.

Users of older iPhone and iPad devices should download the iOS 12 update as soon as possible. The updated version of the company’s 2018 operating system addresses a critical vulnerability that Apple recently patched in iOS 15. The WebKit flaw, according to a support document, could have allowed a website to run malicious code on your device. Apple says it is “aware of a report that this issue may have been actively exploited,” in its usual terse manner.

As a result, if you’re still using an iOS 12 device, you should download the update as soon as possible. This list includes the iPhone 5s, iPhone 6, iPad Air, iPad Mini 2 and iPad Mini 3. You can get iOS 12.5.6 by going to the Settings app, selecting “General,” and then “Software Update.”