An exploit on Hyperbridge, a cross-chain communication protocol built on the Polkadot (DOT) network, resulted in a loss of approximately $237,000. The attacker manipulated a vulnerability in the gateway contract, the digital checkpoint that validates messages moving between blockchains, to gain administrative control over Polkadodot's token contract on Ethereum (ETH). The breach was flagged by security firm CertiK and resulted in one billion tokens being minted and sold. The vulnerability was caused by a forged "proof" from a previously legitimate transaction, which led to insufficient checks in the admin-change function.