A scan of nearly one million smart contracts has identified 34,200 vulnerable contracts that can be exploited to steal Ether. Smart contracts are a set of coded operations that get executed automatically when someone sends an input to the contract. A hacker exploited one such bug in the summer of 2016 to steal over $50 million worth of Ether from TheDAO organization. Researchers from National University of Singapore (NUS) created a tool named Oyente that could scan for bugs in smart contracts for bugs. They initially used Oyente to analyze 19,366 contracts, discovering that 8,833 were vulnerable.
Source: https://www.bleepingcomputer.com/news/cryptocurrency/researchers-find-34-200-vulnerable-ethereum-smart-contracts/