According to reports, it seems that Apple has fixed the problem server side meaning that there is nothing you have to do as the problem appears to have been addressed. For those wondering what the problem was, basically through what seemed like a loophole/security exploit of sorts, a non-authorized user will be able to pull contact information and photos by launching Siri and asking it to access Twitter.
The only caveat to this security flaw is that the user needs to have enabled Siri for photos and Twitter, so if you have never enabled this feature before then chances are you are safe, but if you did, then you would have to disable it, but since it is fixed you can go back to using it just fine. Also the hacker would need to have physical access to your phone in order to do so.
In any case good on Apple for being so speedy with the fix so for now it looks like it’s back to business as usual.