In a Reddit AMA (Ask Me Anything, former AOL’s former CEO Steve Case confirmed that Mark Zuckerberg was a AOL hacker. By stating the following to someone who was apologying for their role in the AOL hacking scene:

Yikes! Well, I’m glad you got this off your chest! 🙂 The hacking of AOL was a real challenge for us. As AOL grew in prominence, it became a big target. Of course, some of the hackers have gone on to do more productive things. It sounds like that is the case with you, and it also was the case with Mark Zuckerberg! Went I first met him 6 or 7 years ago he said he learned how to program by hacking AIM! But, thankfully, rather than focusing on bring AOL down, he shifted to build Facebook up!

Also comments on the reddit comment by ytcracker, pad etc. True OGs

I assumed this story would’ve gotten published by major digital media sites by now. However, only one blog posted about this in 2014.