Electrum version 4.8.2, released on September 11, fixes a Lightning backup export flaw, but the patch does not automatically resolve issues with previously saved backups from certain wallets.
The defect affects Bitcoin wallets with non-deterministic Lightning keys that have opened anchor channels. Older backups from these wallets lack payment-key information needed to recover funds if the channel is closed by the peer.
Which Wallets Are Affected
Two conditions must both be present for a wallet to be affected: it must have non-deterministic Lightning keys, and the backup must concern an anchor channel.
Non-deterministic keys cannot be recreated from a wallet's seed. Wallets based on BIP39 seeds or those with imported extended private keys (xprvs) always have non-deterministic Lightning keys. Electrum-seed wallets created in version 4.1 or later have deterministic Lightning keys, while those created in version 4.0.x do not.
Desktop wallets mark non-recoverable Lightning channels on the wallet information screen, and Android wallets display a warning in the channel-opening dialog.
What the Fix Does
Version 4.8.2 fixes the issue by retaining a randomly generated Lightning private key that was previously deleted during exports. Without this key, older backup files lack the information needed to sweep outputs from anchor channels closed by a peer.
The update also removes the option to request a remote force-close when a backup cannot sweep the resulting output, preventing users from initiating a close they cannot recover funds from.
Steps for Affected Users
Electrum's documented remedy requires users to create fresh exports of their wallet data. Affected wallets display a startup warning upon upgrading.
However, creating a new backup depends on retaining the original wallet data needed for the export. Simply upgrading to version 4.8.2 does not guarantee recovery of key material that may have already been lost.
