Cross-Site Scripting (XSS) flaws are still among the most dangerous threats to web applications. Recently, a critical security vulnerability, CVE-2023-49034, was uncovered in ProjeQtOr 11..2, a popular project management software. This vulnerability allows a malicious remote attacker to execute arbitrary JavaScript code within the victim’s browser by exploiting flaws in HTML data validation.

In this post, I’ll break down the vulnerability, give a clear proof-of-concept exploit, and share trusted references. We’ll focus on clear explanations to help developers and security leaders understand and mitigate this issue.

What is CVE-2023-49034?

CVE-2023-49034 is a Cross-Site Scripting (XSS) vulnerability found in the checkvalidHtmlText function, which is called by both ack.php and security.php files in ProjeQtOr version 11..2. If a remote attacker sends a specially-crafted payload, this function fails to properly sanitize user input, letting the attacker execute arbitrary JavaScript in the victim’s browser.

How Does the Exploit Work?

The core issue is that the function checkvalidHtmlText, which is supposed to check and clean HTML input, doesn’t filter dangerous scripts reliably. When such user-supplied content is echoed back to the browser (like in notifications, alerts, or dashboards), any payload embedded inside will be interpreted and executed by the browser.

An attacker can leverage this by submitting a specially-crafted input containing JavaScript code—for example, in a project comment field, ticket, or any form handled by these vulnerable files.

Below is a simplified version of how the vulnerable function might appear

// File: ack.php or security.php (simplified example)
include_once('somepath/checkvalidHtmlText.php');

$user_input = $_POST['description']; // User input field

if (checkvalidHtmlText($user_input)) {
    // ... process input
    echo $user_input; // Unsafely output to browser
}

The function checkvalidHtmlText() is intended to validate safe HTML, but in version 11..2 it fails to strip out script tags and event handlers robustly.

Exploit Example (Proof of Concept)

Let’s see how an attacker might exploit this. Assume the attacker submits the following comment or data into a susceptible field:

<img src="x" onerror="alert('XSS by CVE-2023-49034')">

Simple Exploit Request (with curl)

curl -X POST http://target-projeqtor-app/ack.php \
  -d "description=<img src='x' onerror='alert(1)'>"

Defacement: Malicious scripts could alter the UI or show fake login forms.

- Information Theft: Sensitive project data may be accessed or exfiltrated using XHR in injected JS.

Update Immediately: If you use ProjeQtOr 11..2, check for a patched release and upgrade ASAP.

2. Sanitize Input: All HTML or user-supplied data should be sanitized using a library like HTMLPurifier.

Mitigation Example in PHP

echo htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8'); // Safe output

References & More Reading

- National Vulnerability Database Entry – CVE-2023-49034
- ProjeQtOr Official Website
- Common Exploits of XSS (OWASP)
- Github PoC / Security Advisory *(check for actual advisories as they are published)*
- HTMLPurifier PHP Library

Final Thoughts

This vulnerability shows how important it is to strictly sanitize and validate user input, especially in software that will be used by multiple users and teams. If you’re responsible for a ProjeQtOr server, patch and review your installation without delay. If you’re developing PHP web apps, always escape untrusted data on output, and consider using well-known libraries for security tasks.

Stay safe online! If you found this helpful, share it with your team.

*This analysis is exclusive and based on the latest available info as of June 2024. For questions or professional audits, contact your preferred security expert.*

Timeline

Published on: 02/20/2024 21:15:07 UTC
Last modified on: 08/29/2024 20:35:37 UTC