This week’s newsletter warns about a severe vulnerability in uses of Libbitcoin’s Bitcoin Explorer (bx) tool, summarizes a discussion about the design of denial-of-service protection, announces a plan to begin testing and collecting data about HTLC endorsement, and describes two proposed changes to Bitcoin Core’s transaction relay policy. Also included are our regular sections with the summary of a Bitcoin Core PR Review Club meeting, announcements of new releases and release candidates, and descriptions of notable changes to popular Bitcoin infrastructure software.