WordPress Plugin LifterLMS 4.21.1 - Access Other Student Grades/Answers via IDOR

# Exploit Title: WordPress Plugin LifterLMS 4.21.1 - Access Other Student Grades/Answers via IDOR
# Date: 2021-05-17
# Exploit Author: captain_hook
# Vendor Homepage: https://lifterlms.com
# Software Link: https://lifterlms.com
# Version: 4.21.1
# Tested on: any

Description

The plugin was affected by an IDOR issue, allowing students to see other student answers and grades

Proof of Concept

- Add 2 users with Student role for the scenario .
- Create A course With a quiz ( I picked True or Flase question for my quiz)
- Set Enrol on Free ( for the ease of scenario )
- Enrol into the Course with Student B and submit your answer to the Course .

The plugin will give a token like :
https://soft-dream.myliftersite.com/quiz/%d8%ac%d9%85%d8%b9-quiz/?attempt_key=wYK
To Check your answer was true or false.

Now Login as a Student A and Enroll in the Course. You can just use
the URL https://soft-dream.myliftersite.com/quiz/%d8%ac%d9%85%d8%b9-quiz/?attempt_key=wYK
and reach the Student B answer.

Fixed in version 4.21.2✓

References

https://make.lifterlms.com/2021/05/17/lifterlms-version-4-21-2/