Wow, I would have figured due to the sugar content they would have lasted for eternity! Was there damage to the packaging? Seems like there are other types of cookies from around 2007 that were also rancid if I remember right. Maybe the packaging contractors used poor handling/ packaging procedures when they re-packaged these items.
I had several rancid items before, but only when they were high in fat. Even the German hart crackers can become rancid due to their high calories (>400kcal) made by butter inside.
The package was fine, no obviously damage/puncture.