It's after they disclosed a serious vulnerability yesterday, that could allow hackers to take complete control of your device.
Apple are advising users to go to settings, hit "general" and click "software update".
Apple said the vulnerability affects iPhones dating back to the 6S model, iPad 5th generation and later, iPad Air 2 and later, iPad mini 4 and later, all iPad Pro models and the 7th generation iPod touch.
