Fetch.ai

ai’s TokenConversionManagerV3 conversionIn() relied on an ECDSA signature from a single authorizer as its principal authorization mechanism. After obtaining that authorizer’s private key, the attacker signed a fresh conversion message for an attacker-controlled recipient and called conversionIn().

Unlike conversionOut(), the function lacked the checkLimits(amount) restriction and did not independently require proof that corresponding assets had been burned or locked on the other side of the conversion. The valid signature was therefore sufficient to release the converter’s entire remaining FET inventory in one transaction.