The actor Jennifer Lawrence had her account hacked and has already confirmed that topless photos were real. Apple tell us that..
So basically, having security questions with answers that people can find out easily (via Facebook / Twitter or your online profile elsewhere) is a bad idea. Although everyone knows this already, unfortunately people will still continue to be hacked for some time to come. Get more information here or read the full announcement below.
Update to Celebrity Photo Investigation
We wanted to provide an update to our investigation into the theft of photos of certain celebrities. When we learned of the theft, we were outraged and immediately mobilized Apple’s engineers to discover the source. Our customers’ privacy and security are of utmost importance to us. After more than 40 hours of investigation, we have discovered that certain celebrity accounts were compromised by a very targeted attack on user names, passwords and security questions, a practice that has become all too common on the Internet. None of the cases we have investigated has resulted from any breach in any of Apple’s systems including iCloud® or Find my iPhone. We are continuing to work with law enforcement to help identify the criminals involved.
To protect against this type of attack, we advise all users to always use a strong password and enable two-step verification. Both of these are addressed on our website at http://support.apple.com/kb/ht4232.