But even anchor inputs don’t solve the whole problem of closing fees. When a Lightning Network’s closing transaction fee gets bumped up, there’s a possible security issue. By way of a fee-bumping technique known as “Child Pays For Parent” (CPFP), a so-called “child” transaction pays too little for a fee, and so a “parent” transaction spends the same coins as the child it’s referring to, bumping up the fee. There’s a possible issue where, even if users try to bump up the fee, nodes might ignore the transaction if the parent transaction’s fee is still too small. In that scenario, the fee is not successfully bumped up, meaning the transaction doesn’t go through as fast as the user needs it to.