Blockchain security researcher Specter discovered that Tether blacklisted a MetaMask Swap router contract address in 2021, with the restriction remaining active for nearly five years. The finding emerged during an investigation into the Payy Network attack. Specter noted that this long-standing blacklist status had not been previously identified despite the contract's integration with one of crypto's most widely used wallets. The discovery highlights potential legacy restrictions within DeFi infrastructure that may persist undetected for extended periods.