The founder of 4chan, Christopher Poole, aka “moot” has confirmed few hours ago, in a blog post. The hacker was able to access the Pass credentials of three 4chan Pass (paid account without CAPTCHAs system) users, who have been notified by the company shortly after the discovery of the attack and offered refunds along with the lifetime Passes. The motive behind the hack was to expose the posting habits of a specific user the attacker didn’t like, moot wrote.
Source: https://thehackernews.com/2014/04/4chan-Hacked-Image-Bulletin-Board.html