SlowMist: All five forged receipts in the Ankr cross-chain bridge attack carried valid signatures.

Ankr's cross-chain bridge lost roughly $304,500 after an attacker submitted five forged cross-chain receipts that all carried valid signatures from the bridge's trusted consensus signers, according to SlowMist. The attacker referenced a single legitimate Optimism transaction and altered the recipient, token and withdrawal amount in each receipt. The bridge's withdrawal function released assets without independently verifying the actual source-chain event, which allowed the fraudulent claims to pass. The source of the unauthorized signatures is still under investigation, and SlowMist has not confirmed whether a signer was compromised. Watch for Ankr's post-mortem on signer key management and whether the bridge adds independent source-chain event verification to its withdrawal logic.