Bitcoin wallet bug let rogue servers steal funds when users tried to speed up payments

A bitcoin wallet security flaw allowed malicious servers to trick users into signing payments to attackers when they tried to speed up transactions, with developers confirming at least one case in which money was stolen. Electrum, one of Bitcoin's oldest software wallets, disclosed the vulnerability on Saturday , saying some servers were already exploiting it. The developers received two reports in October, including one from a user who lost funds after approving what appeared to be a routine transaction-fee increase. The attack exploited how Electrum handles bitcoin payments not yet confirmed by the network. Unlike a full Bitcoin node, Electrum relies on outside servers to retrieve transaction histories and broadcast payments. Before the fix, the wallet trusted those servers to report pending transactions without verifying their signatures.

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