The passwords were shared via a Russian hacker site, and security researcher Per Thorsheim confirms that the leak is legit.
LinkedIn hasn’t offered any statement on the incident at the time of this writing, but we would strongly suggest changing your password.
UPDATE: LinkedIn reports via Twitter that its “team is currently looking into reports of stolen passwords. Stay tuned for more.”
UPDATE 2: LinkedIn tweets again — “Our team continues to investigate, but at this time, we’re still unable to confirm that any security breach has occurred. Stay tuned here.”