This critical flaw CVE-2016-4631 resides in the ImageIO, the API used to handle image data in almost every Apple operating system, including Mac OS X, watchOS, and tvOS. The attack scenario is simple as efficient, the attacker just needs to send the malicious exploit code to the victims device via a multimedia message (MMS) or iMessage inside a Tagged Image File Format (TIFF) When the victims will receive the malicious message, the exploit will be executed. This means that your Wi-Fi passwords, login credentials, and email logins could be easily compromised in the attack.”]
Source: http://securityaffairs.co/wordpress/49542/hacking/hacking-apple-cve-2016-4631.html