Bitcoin wallet bug let rogue servers steal funds when users tried to speed up payments
Summary
Electrum disclosed a vulnerability that let malicious servers substitute fake unconfirmed Bitcoin transactions in users’ wallet histories. When users tried to speed up a substituted payment with Replace-by-Fee, the wallet could sign a valid replacement sending funds to the attacker. Developers confirmed at least one theft, though they did not reveal the amount or identify the servers. Electrum released version 4.8.3 on Oct. 24 to verify signatures on unconfirmed transactions spending users’ coins. Users of older versions may remain vulnerable when connected to malicious servers; upgrading and checking payment details before signing are recommended.
