Electrum 4.8.3 fixes flaw that let servers trick users into paying attackers

The story so far: Electrum wallet security flaw

Electrum disclosed a high-severity flaw, fixed in version 4.8.3, that lets a malicious server swap a just-broadcast transaction for one paying an attacker, with RBF fee bumps sending funds to the attacker. Some servers already ran the attack and two users reported cases, one losing funds. Electrum released 4.8.3 on 24…

1. 24 Oct 202620:22 UTC

   Electrum says high-severity flaw in versions before 4.8.3 has been exploited, with funds lost

   Electrum says a high-severity flaw fixed in version 4.8.3 lets a malicious server swap a just-broadcast transaction for a conflicting one paying an attacker; raising the fee with RBF then sends the funds to the attacker. Electrum says some servers have already run the attack and two users have reported cases, one of whom lost funds.

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2. 27 Oct 202618:02 UTC

   Electrum 4.8.3 fixes flaw that let servers trick users into paying attackers

   Electrum released version 4.8.3 on 24 October 2026 to fix a security flaw already used in real attacks, in which malicious servers showed fake transactions and induced users to sign payments to attackers when speeding up transactions with RBF, without needing private keys. Electrum said it received two related reports, one user losing Bitcoin after raising the fee, and urged users to update to 4.8.3.

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