https://news.bitcoin.com/lightning-network-developer-warns-about-major-vulnerability-abandons-security-tasks/

Antoine Riard, a Lightning Network (LN) developer, recently disclosed a major vulnerability affecting Bitcoin’s scaling layer. This vulnerability, which was addressed with a series of mitigations, involves a “new transaction-relay jamming attack” that can affect shared funds in channels. Riard abandoned LN-related work after testing the feasibility of these attacks in the open.

"I think this new class of replacement cycling attacks puts lightning in a very perilous position, where only a sustainable fix can happen at the base-layer, e.g adding a memory-intensive history of all-seen transactions or some consensus upgrade."