function once(fn) {
  let called = false;
  return (...args) => {
    if (called)
      return;
    called = true;
    fn(...args);
  };
}
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.