iPhone 4S Siri ships with security flaw

The trouble is that even if you have a passcode set on your iPhone's lockscreen, Siri can bypass it and get into your phone. This is not unlike the trouble Apple had with emergency calls being able to bypass lockscreen security and gain access to your photos and contacts. This time around, Apple has Siri enabled on the lockscreen by default, meaning anyone can use a voice command to access your e-mail, contacts or calendar. 

As we mentioned, if you have nothing that requires too much security in any of those systems, it's not much of a worry ("Oh no! I left my phone on the bus and now the person who has it can e-mail my mom! My mom!") Of course, if it's that much of a worry for you, all you have to do is disable Siri from your lockscreen in the "Passcode Lock" settings screen. 

source: CNet