  constructor(seqno, onPayload) {
    this.inSeqno = seqno;
    this._onPayload = onPayload;
    this._len = 0;
    this._lenBytes = 0;
    this._packet = null;
    this._packetPos = 0;
  }
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.