Got an iPhone? Update it. Right now. This is not a drill.
Software exploiting that vulnerability was found "targeting an activist's iPhone in the Middle East," the Associated Press reports. Once a flaw like that is out there, it's only a matter of time before other hackers start using it. So be proactive and patch up your phone before they have the chance.
To update your iPhone, open Settings, then General, then Software Update, then "Install." (iOS 9.3.5 is the version you want.)