The vulnerability is similar to the Stagefright vulnerabilities, discovered a year ago in Android, that allowed hackers to silently spy on almost a Billion phones with just one specially-crafted text message. The bug (CVE-2016-4631) actually resides in API used to handle image data and works across all widely-used Apple operating systems, including Mac OS X, tvOS, and watchOS. Users are advised to patch their devices as it would not take enough time for bad actors to take advantage of the vulnerabilities, which are now known.
Source: https://thehackernews.com/2016/07/iphone-hack-exploit.html