manager/templates/default/images/modx-theme/form/button-bg-over.svg
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg version="1.1" xmlns="http://www.w3.org/2000/svg">
<defs>
<linearGradient id="gradient" x1="0" x2="0" y1="0" y2="1">
<stop offset="0%" stop-color="#ffffff"/>
<stop offset="100%" stop-color="#dfdfdf"/>
</linearGradient>
</defs>
<rect x="0" y="0" height="100%" width="100%" fill="url(#gradient)" />
</svg>