[Attestation](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase1/beacon-chain.md#extended-attestation) had `custody_bits_blocks`: ``` custody_bits_blocks: List[Bitlist[MAX_VALIDATORS_PER_COMMITTEE], MAX_SHARD_BLOCKS_PER_ATTESTATION] ``` It's used by [is_valid_fraud_proof](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase1/shard-transition.md#verifying-the-proof). Looks like it was dropped during recent merge: it's missing [here](https://github.com/ethereum/eth2.0-specs/blob/a0175ca1b353a1271703bb66f262b9b1e9a4adcc/specs/phase1/beacon-chain.md#extended-attestation). But is present [here](https://github.com/ethereum/eth2.0-specs/blob/50ac8ebb0ccebb0ced41e0471498c422db816856/specs/phase1/beacon-chain.md#extended-attestation).
Attestation had
custody_bits_blocks:It's used by is_valid_fraud_proof.
Looks like it was dropped during recent merge: it's missing here. But is present here.