Exploit turns Siri into a blabbermouth, allowing hackers to use your contacts list to send messages
Once you type something along the lines of "Call A," Siri opens up your contacts list. This allows anyone to have access to it. Emails can be sent from your address telling your boss off, or insulting your best friend's wife. Ironically, the exploit was not available on those iPhone units that didn't use the passcode lockscreen feature.
It is possible that in a future update, we will see Siri divorced from the passcode. But for now, you can manually shut down Siri's integration with the passcode lockscreen by going into the Touch ID and Passcode settings in iOS 7. Toggle the switch to off under "Allow Access When Locked," and Siri will keep her mouth shut when it comes to your contacts.
source: NBCNews via Gizmodo