Bitcoin Optech Newsletter #420

This week's Bitcoin Optech Newsletter provides several crucial updates for the Bitcoin ecosystem. It relays an advance notice regarding a planned Core Lightning (CLN) security release, version v26.06.7. This security update will initially be released in an embargoed manner, meaning binaries will be available immediately but source code will be withheld for 14 days to mitigate potential exploitation. CLN operators preferring to wait for source code availability are advised to restart their nodes using the `--offline` flag to maintain onchain enforcement while preventing peer connections. The newsletter also summarizes a significant discussion on Delving Bitcoin concerning the implementation of a universal opt-in replay protection mechanism for potential future Bitcoin forks. This proposal, stemming from recent replay attack incidents on minority chains, suggests using the taproot annex to commit a 34-byte payload containing the previous block hash or, alternatively, a block height and hash suffix. Furthermore, the newsletter notes that the Hardware Wallet Interface (HWI) project, a critical tool for interacting with hardware wallets, is transitioning into maintenance mode. Lastly, it describes a request for comments on the use of block-range filters, along with regular announcements of new releases and release candidates for popular Bitcoin infrastructure software.