<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
   <defs>
      <filter id="filter">
         <feGaussianBlur in="SourceAlpha" stdDeviation="0" result="blur"/>
         <feMerge>
            <feMergeNode in="blur"/>
            <feMergeNode in="SourceGraphic"/>
         </feMerge>
      </filter>
   </defs>
   <rect x="0" y="0" width="100" height="100" fill="red"/>
   <rect x="0" y="0" width="100" height="100" filter="url(#filter)" fill="green"/>
</svg>