Wanchain's Cardano cross-chain bridge suffered a significant security breach, resulting in the theft of approximately 515 million NIGHT tokens from its treasury. BlockSec's monitoring revealed that the attack exploited a vulnerability in the TreasuryCheck validator's signature message encoding. The issue arose from the raw concatenation of 14 variable-length redemption fields without delimiters, allowing different field combinations to produce identical byte strings and reuse the same hash and signature. BlockSec confirmed the vulnerability by analyzing the on-chain Plutus V2 bytecode and decoding the attack transaction's redemption data. The use of Sha3_256(SerialiseData(...)) could have prevented this by providing clear CBOR-encoded field boundaries, thus avoiding field-splitting signature reuse attacks.