<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="100" height="100">
  <defs>
    <filter id="DropShadow" x="-50%" y="-50%" width="200%" height="200%" >
      <feOffset in="SourceGraphic" dx="10" dy="10" result="Offset"/>
      <feDropShadow in="SourceGraphic" x="10" y="10" width="40" height="40" dx="10" dy="10" stdDeviation="10" flood-color="red" result="Drop"/>
      <feComposite operator="over" in="Drop" in2="Offset" />
    </filter>
  </defs>

  <rect filter="url(#DropShadow)" x="10" y="10" width="40" height="40" fill="green"/>
</svg>