A vulnerability in nimiq-block prior to version 1.7.2 allows a malicious validator to bypass the skip block quorum verification by exploiting out-of-range BitSet indices and u16 truncation. This flaw enables an attacker with fewer than the required 2f+1 signer slots to pass verification by duplicating a single BLS signature. The issue is fixed in version 1.7.2, and no workarounds are currently known.