A MetaMask Swap routing contract address was added to Tether's blacklist in 2021 and remained restricted for nearly five years, blockchain security researcher Specter said while investigating the Payy Network attack. The status had not previously been identified despite the contract's integration with MetaMask, one of the crypto industry's most widely used wallets. The finding points to legacy restrictions in decentralized-finance infrastructure that can remain undetected for extended periods.