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Cyber Security Academy · Lesson

File Upload and SSRF Vulnerabilities

Bypass file upload restrictions, exploit SSRF to access internal services, and chain vulnerabilities.

File Upload Vulnerabilities

File upload functionality is one of the highest-risk features in web apps. Insufficient validation allows uploading executable files (PHP, JSP, ASPX) that the server then executes — leading to remote code execution.

Basic Upload Bypass: Extension Filtering

Client-side and blacklist-based extension filters are bypassable. Try: double extensions (.php.jpg), case variations (.PhP), null bytes (file.php%00.jpg), and alternative extensions (.php5, .phtml, .phar).

# Try alternative PHP extensions:
file.php
file.php5
file.phtml
file.phar
file.php.jpg
file.php%00.jpg
file.PhP

# ASP/ASPX alternatives:
file.asp
file.aspx
file.asa
file.cer

All lessons in this course

  1. Burp Suite Proxy and Intercepting Requests
  2. Testing for Injection Vulnerabilities
  3. Authentication and Session Testing
  4. File Upload and SSRF Vulnerabilities
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