Apple has released a software update to iOS and macOS that you should download right away.
The security update patches a dangerous vulnerability in WiFi chips that allows hackers to "execute arbitrary code" - industry-speak for taking over your device. Through the WiFi chip, a hacker may be able to assume control of your device's processor, the central computer that runs everything else.
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.
Artenstein will be presenting the details of his findings at the Black Hat security conference next week.