Malicious Electrum servers trick wallet users into signing forged zero-fee Bitcoin transactions

AI-assisted source summary · not independently verified. Content standards

Malicious Electrum servers replace users' just-broadcast Bitcoin transactions with forged zero-fee transactions paying similar addresses, tricking users into fee-bumping and signing them by exploiting a high-severity vulnerability in older versions that failed to verify signatures on mempool transactions. Electrum released 4.8.3 on October 24, adding checks for signatures on inputs owned by the wallet, and published the GHSA-6jp4-8v48-cc5v advisory requiring users to upgrade. Users unable to upgrade should verify the recipient address and amount before signing, including fee-bumping operations; users who connect only to their own servers are unaffected.