Electrum Releases Version 4.8.3 to Fix Bitcoin Wallet Flaw Exploited by Malicious Servers

Electrum has released version 4.8.3 of its Bitcoin wallet software to patch a critical vulnerability tracked as GHSA-6jp4-8v48-cc5v that allowed malicious servers to steal funds through transaction substitution. The flaw enabled compromised servers to replace legitimate unconfirmed outgoing transactions with attacker-controlled transactions displayed with zero fees. When users attempted to raise fees using Replace-By-Fee, they inadvertently signed transfers directly to attackers. Developers confirmed actual losses occurred following a user report on October 18, with at least two users reporting attacks. The update mandates signature verification for unconfirmed transactions spending wallet-owned UTXOs.