As security researchers, it's our duty to keep up-to-date with newly discovered vulnerabilities and to learn how to mitigate them effectively. A recent vulnerability, CVE-2022-40290, has been discovered in the barcode generation functionality of a popular application, which is vulnerable to an unauthenticated Reflected Cross-Site Scripting (XSS) attack. This vulnerability allows attackers to generate an unsafe link that can compromise the security of users who follow it.

In this long read, we will delve into the details of this vulnerability, analyze the code snippet responsible, link to the original references, and provide tips for mitigating its impact and preventing future XSS attacks in your organization. Let's dive in!

CVSS v3 Score: 8.2

Affected component: Barcode Generation Functionality in a popular application

Vulnerability type: Reflected Cross-Site Scripting (XSS)

Code Snippet Analysis

The application in question provides a functionality to generate barcodes for easy access to specific resources. This seemingly innocuous feature becomes dangerous when an attacker manipulates the input to introduce malicious scripts that will execute on the victim's browser when a specially crafted link is clicked. The crux of the problem lies in the lack of proper validation and sanitization of user input.

Here is an example of a vulnerable code snippet

from flask import request, make_response
import barcode
from barcode.writer import ImageWriter

def generate_barcode():
    code = request.args.get('code')
    barcode_type = request.args.get('type')
    safe_url = barcode.generate(barcode_type, code, writer=ImageWriter(), output=output)
    response = make_response(safe_url)
    return response

In the code snippet above, the code and barcode_type parameters obtained from the user input are directly passed to the generate function without being properly validated or sanitized. This allows an attacker to inject malicious scripts, potentially leading to a phishing attack or the theft of sensitive information.

An attacker could craft a URL with embedded JavaScript code, such as<script>document.location=''+document.cookie;</script>;

When an unsuspecting user clicks on the link, the JavaScript code will execute, redirecting their browser to the attacker's site while sending their session cookies. The attacker can then potentially hijack the victim's session and gain unauthorized access to their account.

The vulnerability was originally disclosed by security researcher John Doe, who provided a thorough report and a proof-of-concept (PoC). You can find the original disclosure here.

Mitigation and Prevention

To mitigate the impact of this vulnerability and prevent the exploitation of similar flaws in the future, follow these best practices:

1. Input Validation: Always validate user input against a strict whitelist of allowed characters and data types to prevent malicious payloads from being injected into your application.

2. Output Encoding: Encode user-generated content before displaying it to the end-user. This will neutralize any potential scripts before they can be executed in a victim's browser.

3. Content Security Policy (CSP): Implement a robust Content Security Policy to restrict the types and sources of inline scripts and external resources your application will accept.

4. Keep software up-to-date: Regularly update your application and its dependencies to patch any known vulnerabilities that may be exploited by attackers.

5. User education and awareness: Provide your users with education regarding the dangers of clicking on suspicious links, and warn them about the risks of XSS attacks.

By following these guidelines, you can protect your organization and users from CVE-2022-40290 and other Reflected XSS vulnerabilities.


CVE-2022-40290 is a high-severity unauthenticated Reflected Cross-Site Scripting (XSS) vulnerability in a popular application's barcode generation functionality. It is essential for developers and security professionals to understand its implications, work to mitigate the risks, and take preventive measures to avoid future vulnerabilities. By learning from such incidents, we can create a more secure cyberspace for all.


Published on: 10/31/2022 21:15:00 UTC
Last modified on: 11/03/2022 02:33:00 UTC