V3 Transactions are still vulnerable to significant tx pinning griefing attacks

Child Pays for Parent (CPFP) is a method used in cryptocurrency transactions to expedite the confirmation of a transaction by paying higher fees. The typical scenario involves using one or possibly two unspent transaction outputs (UTXOs) to cover the necessary fee. While it was previously misunderstood that version 3 (V3) transactions could consolidate multiple parent transactions into a single large transaction, this is not possible due to restrictions on unconfirmed inputs. Therefore, the substantial limit placed on the number of inputs for CPFP seems unnecessary under normal circumstances.

In the realm of Bitcoin's Lightning Network, current practices employ signed anchors for establishing channel states, an approach already implemented in anchor channels. These anchors can have zero value; however, the security aspect is maintained as only the intended parties can spend them due to the requirement of their signatures. It has been pointed out that the existing Lightning anchor channels are not optimized, as they use two anchor outputs where one would suffice. This inefficiency is highlighted with references to discussions and contributions made by Peter Todd, a notable figure in the cryptocurrency development community, who addresses the redundancy of remote anchors in anchor channels and suggests that a single anchor output is adequate for such purposes. Further details and discussion can be found through resources like the Linux Foundation mailing list and direct communication with Todd himself.