WordPress AMP Toolbox 1.9.4 Cross Site Scripting

Class Input Validation Error
Remote Yes

Credit Ricardo Sanchez
Vulnerable AMP Toolbox Plugin 1.9.4

AMP Toolbox Plugin is prone to a stored cross-site scripting
vulnerability because it fails to sufficiently sanitize user-supplied data.

An attacker may leverage this issue to execute arbitrary script code in the
browser of an unsuspecting user in the context of the affected site. This
may allow the attacker to steal cookie-based authentication credentials and
to launch other attacks.

To exploit this issue following steps:
The XSS reflected because the values are not filter correctly:

Demo Request:
http://localhost/wordpress/wp-content/plugins/amp-toolbox/
css-tidy/css_optimiser.php?template=demo&css_text=1&url=”
><script>alert(“XSS”)</script>&custom=1&lang=e&preserve_css=1