osTicket 1.12 - Persistent Cross-Site Scripting via File Upload

# Exploit Title: osTicket-v1.12 Stored XSS via File Upload
# Vendor Homepage: https://osticket.com/
# Software Link: https://osticket.com/download/
# Exploit Author: Aishwarya Iyer
# Contact: https://twitter.com/aish_9524
# Website: https://about.me/aish_iyer
# Category: webapps
# CVE: CVE-2019-14748

1. Description

An issue was discovered in osTicket before 1.10.7 and 1.12.x before 1.12.1.
The Ticket creation form allows users to upload files along with queries.
It was found that the file-upload functionality has fewer (or no)
mitigations implemented for file content checks; also, the output is not
handled properly, causing persistent XSS that leads to cookie stealing or
malicious actions. For
example, a non-agent user can upload a .html file, and Content-Disposition
will be set to inline instead of an attachment.

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-14748

2. Proof of Concept

Steps to Reproduce:
- Login to the portal as a non agent user:
- Open a New Ticket
- Select  any option from the dropdown menu present under "Help Topic"
- Text box appears, enter details accordingly
- In the section "drop files here or choose them", we would be putting our
payload
- Open any text editor  and name the file as test(say) with .html extension.
- Within the file, enter the payload
<script>alert(document.cookie);</script>
- Save the test.html file.
- Now click on drop files here option and enter the test.html file.
- Click on "create ticket" option
- Login with another user(agent)
- Now within the User Directory, go to the user under which the payload has
been put.
- The ticket raised with the name mentioned will be shown under the subject
category.
- Scroll down and the file uploaded will be present below.
- Click on the file, and the payload gets executed which is persistent

3. Reference

https://github.com/osTicket/osTicket/commit/33ed106b1602f559a660a69f931a9d873685d1ba
https://github.com/osTicket/osTicket/releases/tag/v1.12.1
https://github.com/osTicket/osTicket/releases/tag/v1.10.7

4. Solution

The vulnerability has been patched by the vendor in the next release which
is osTicket v1.10.7.