Live Nation, the parent company of Ticketmaster, revealed that it was the victim of a cyber attack that compromised user data.The company said in a filing with the U.S. Securities and Exchange Commission that it discovered an "unauthorized activity within a third-party cloud database," on May 20 and promptly launched an investigation.A week later, "a criminal threat actor offered Live Nation what it alleged was user data for sale via the dark web," according to the filing.