Bridge Exploit
An attack on the software that moves assets between blockchains, usually by faking the proof that a deposit happened on the other chain.
A common bridge design locks the real asset in a contract on one chain and mints a claim token on another, with a set of validators or a verification contract attesting that the deposit occurred. The two recurring failure points are compromise of the attesting keys, letting an attacker sign a withdrawal that never had a deposit, and a flaw in signature or proof verification, letting an attacker mint claims out of nothing. Because bridges pool deposits from many users into a single contract, they present a large and static target, and several of the largest single thefts in the sector have been bridge exploits. The 2022 attacks on the Ronin bridge, through compromised validator keys, and on Wormhole, through a signature-verification flaw, are well documented examples.
In practice
When unbacked claim tokens are minted on the destination chain, the attacker typically sells them into liquidity pools, leaving other holders with tokens whose backing no longer exists.
The common misunderstanding
That a bridged token is the same asset as the native one, when it is a claim whose value depends entirely on the bridge remaining solvent, honest, and unexploited.