GHSA-6973-8887-87FF nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation

Impact SkipBlockProof::verify computes its quorum check using BitSet.len, then iterates BitSet indices and casts each usize index to u16 slot as u16 for slot lookup. If an attacker can get a SkipBlockProof verified where MultiSignature.signers contains out-of-range indices spaced by 65536, these...