<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<filter id="blur">
<feGaussianBlur stdDeviation="3"/>
</filter>
<clipPath id="clip">
<rect x="20" y="20" width="140" height="140"/>
</clipPath>
</defs>
<g filter="url(#blur)" clip-path="url(#clip)">
<rect width="180" height="180" fill="green"/>
<rect x="40" y="40" width="100" height="100" fill="blue"/>
</g>
</svg>