To take advantage of the flaw, known as Broadpwn, all an attacker has to do is get within range of your WiFi device, according to Nitay Artenstein, the security researcher at Exodus Intelligence who discovered the problem and reported it. The flaw affects millions of Apple and Android devices; Google's Android team released a patch for that platform earlier this month.
To update your iOS software, head to Settings > General > Software Update. You'll see either a message informing you that your software is up to date, or a prompt to download iOS 10.3.3. If you're on a Mac, open the App Store and click on the Updates tab.