Seeing as CNN never met a terrorist or murdering dictator that they didn't like, they probably bought the journal from one of the terrorists who attacked the consulate that night.
It's not outside reality that the Tripoli CNN office got a call on the 8th or 9th about how if they wanted a good story, to be outside the Benghazi consulate the morning of the 11th. How often have they been willing to follow the bad guys to get a shot of them ambushing our troops?
I seem to recall at least once in Iraq or the 'Stan. Naturally, since they weren't promptly taken out and shot, they figure if they are careful, they can scoop the competition.