The good news is that I haven't heard of mass attacks (yet) using these attacks. The bad news is that it typically doesn't take long for those to start once the Bad Guys know that something is possible.
The attack sends a web link to a page that contains malware. This malware is unpleasant - it's the first remote jailbreak exploit, so it basically takes total control of you iDevice.
In your iPhone (and iPad), click the "Settings" app, then "General" then "Updates" and select "Check for updates". You want iOS 9.3.5. I'm not sure if this applies to iPads as well but recommend that you check.
Like I said, I expect there's a Bad Moon rising. We'll likely see mass exploitation of this in a few days.