A bug exploit is the deliberate use of a flaw, or bug, in software to make it behave in a way its designers did not intend, usually to gain money, data or control. In crypto, exploits most often target smart contracts in decentralized finance protocols and bridges, where errors in code can let attackers withdraw funds, mint unbacked tokens or manipulate prices, sometimes using flash loans to borrow large sums for a single transaction. Famous cases include the 2016 DAO attack on Ethereum, which led to a hard fork, and several bridge exploits worth hundreds of millions of dollars. Whether exploiting a bug is legal depends on the jurisdiction and facts, but courts have treated many cases as theft or fraud. Projects defend with audits, testing and a bug bounty. Also see Black Hat Hacker.
Last updated 13 Nov 2026