"If you receive a text message on your iPhone any time after Thursday afternoon containing only a single square character, Charlie Miller would suggest you turn the device off. Quickly.
That small cipher will likely be your only warning that someone has taken advantage of a bug that Miller and his fellow cybersecurity researcher Collin Mulliner plan to publicize Thursday at the Black Hat cybersecurity conference in Las Vegas."
Evidently, the hack allows the hacker to control all aspects of your iPhone. Not good.