Cybercriminals are sometimes as careless about security as those they attack. An open database exposed a huge fraud scheme impacting vendors such as Groupon and Ticketmaster. Criminals created accounts with the ticket sellers and used stolen credit card data to buy tickets and the resell them online - sometimes multiple times. Researchers found 17 million emails in total, linked to fake accounts from ticket vendor websites. This discovery helped the most impacted company, Groupon, close most of the fraudulent accounts. The database is now offline.