Introduction

This is a review of the Advanced Web Attacks and Exploitation (WEB-300) course and its OSWE exam by Offensive-Security. I’ve taken this course because I was curious about what secret tricks this course will offer for its money, especially considering that I’ve done a lot of source code reviews in different languages already.

This course is designed to develop, or expand, your exploitation skills in web application penetration testing and exploitation research. This is not an entry level course–it is expected that you are familiar with basic web technologies and scripting languages. We will dive into, read, understand, and write code in several languages, including but not limited to JavaScript, PHP, Java, and C#.

I got this course as part of my Offensive-Security Learn Unlimited subscription, which includes all of their courses (except for the EXP-401) and unlimited exam attempts. Luckily, I only needed one attempt to pass the exam and get my OSWE certification.

The Courseware & the Labs

I’d say it’s a typical Offensive-Security course. It comes with hundreds of written pages and hours of video content explaining every vulnerability class in such incredible detail, which is fantastic if you’re new to certain things. But the courseware still assumes a technically competent reader proficient with programming concepts such as object orientation, so I don’t recommend taking this course without prior programming knowledge.

You will also get access to their labs to follow the course materials. These labs consist of Linux and Windows machines that you will pwn along the course, and they are fun! You will touch on all the big vulnerability classes and some lesser-known ones that you usually don’t encounter in your day-to-day BugBounty business. Some of these are:

  • Authentication Bypasses of all kinds
  • Type Juggling
  • SQL Injection
  • Server-Side JavaScript Injection
  • Deserialization
  • Template Injection
  • Cross-Site Scripting (this was unexpected in an RCE context!)
  • Server-Side Request Forgery
  • Prototype Pollution
  • Classic command injection

It took me roughly a week to get through all videos and labs, mostly because I was already familiar with most of the vulnerability classes and content. My most challenging ones were the type juggling (this is some awesome stuff!) and prototype pollution. I also decided not to go the extra miles; however, I’d still recommend this to everyone who is relatively new to source code review and exploitation and wants to practice their skills.

The Exam

Overview

The exam is heavily time-constrained. You have 47 hours and 45 minutes to work through your target machines, where you have full access to the application’s source code. But be prepared that the source code to review might be a lot - good time management is crucial here. After the pure hacking time, you will have another 24 hours to submit your exam documentation.

The Proctoring

But before actually being able to read a lot of source code, you have to go through the proctoring setup with the proctors themselves. You have to be 15 minutes early to the party to show your government ID, walk them through your room and make sure that they can correctly monitor (all of) your screens. You are also not allowed to have any additional computers or mobile phones in the same room.

The proctoring itself wasn’t a real problem. The proctors have always been friendly and responsive. Note that if you intend to leave the room (even to visit your toilet), you have to let them know when you leave and when you return to your desk. But you do not have to wait for their confirmation - so no toilet incidents are expected ;-) If you intend to stay away for a more extended period (sleep ftw.), they will pause the VPN connection.

Basic Machine Setup

After finishing the proctoring setup at around 12:00, the real fun started. Offensive-Security recommends using their provided Kali VMs, but I decided to go with my native macOS instead. Be aware that if you’d choose to go this way, Offensive-Security does not provide you with any technical support (other than VPN issues). I’ve used the following software for the exam:

  • macOS Monterey 12.3.1
  • Viscosity for the VPN connection
  • Microsoft Remote Desktop to connect to the exam machines
  • Notion as my cheatsheet (Yes, you are allowed to use any notes during the exam)
  • BurpSuite Community for all the hacking (You are not allowed to use the Pro version!)
  • Python for all my scripting works

The exam machines come in a group of two, which means you’ll get one development machine to which you’ll have full access and one “production” machine which you don’t have complete access. You’ll have to do all your research and write your exploit chain on the development machine and afterward perform your exploit against the production machine, which holds the required flags.

The development machines have a basic setup of everything you need to start your journey. You don’t need any additional tools (auto-exploitation tools such as sqlmap are forbidden anyways). Another thing: you are not allowed to remotely mount or copy any of the application’s source code to your local machine to use other tools such as the JetBrains suite to start debugging. You have to do this with the tools provided - so make sure that you’ve read the course materials carefully for your debugging setup and you’re familiar with the used IDEs.

Exam Goal

The goal of the exam is to pwn these independent production machines using a single script - choose whatever scripting language you’re comfortable with. This means your script should be able to do all the exploitation steps in just one run, from zero to hero. If your script fails to auto-exploit the machine, it counts as a fail (you might still get some partial points, but it might not be enough in the end). You need to have at least 85 out of 100 points to pass the exam point-wise.

Pwn #1

Once I was familiar with the remote environment, I started to look at target machine #1. It took me roughly 4 hours to identify all the necessary vulnerabilities. Next up: Automation. I started to write my Python script to auto-exploit both issues, but it took much longer than expected. Why? I struggled with the reliability of my script, which for some reason, only worked on every second run. After 2.5 hours of optimizations, I finally got my script working with a 10/10 success rate.

I’ve submitted all the flags, ultimately getting me the first 50 points. At that point, I also started to collect screenshots for the documentation part of the exam.

After I got everything, I went to sleep for about 10 hours (that’s important for me to keep a clear mind), and already having half of the required points got me a calm night.

Pwn #2

After I had breakfast on the second day, I started to look at machine #2, which was a bit harder than the first one. It took me roughly half an hour to spot vulnerability #2, but I still had to find the vulnerability #1. Unfortunately, that also took longer than expected because I’ve followed a rabbit hole for about two hours until I’ve noticed that it wasn’t exploitable. But still, after around 6 hours of hacking, I was able to identify the entire bug chain and exploit it. I’ve submitted both flags, getting me an overall 100 out of 100 points - this was my happy moment!

I wrote the Python exploit for auto-exploitation relatively quickly this time since it was structurally entirely different from machine #1. I also started to collect all the screenshots for my documentation. I went to sleep for another 10 hours.

Documentation

On the last day, my exam was about to end at 11:45, and I started early at 08:00 to be able to double-check my scripts, my screenshots, etc. I improved my Python scripts and added some leet hacker output to them without breaking them (yay!). I finished that part at around 10:00 and had almost 2 hours left in the exam lab. So I started to do my documentation right away and noticed (somewhat last minute) that I was missing two screenshots, and trust me, they are so important!

I informed the proctor to end my exam, and I then had another 24 hours to submit my documentation. The entire documentation took me roughly 8 hours to complete - I’m a perfectionist, and this part always takes me the most time to finish. I sent in the documentation on the same day and completed my exam.

A couple of days later, I received the awaited happy mail from Offensive-Security saying that I’ve passed the exam

netcup-xss

Who Should Take This Course?

The course itself is excellent in its content, presentation, and lab-quality. I haven’t seen any comparable course out there, and while many people are claiming that you can get all of it cheaper using Udemy courses, they are only partially correct. Yes, you’ll find a lot of courses about discovering and exploiting vulnerabilities in black box scenarios, but the AWAE targets a different audience. It is mostly about teaching you the source code’ish way of finding vulnerabilities. Where else do you have the chance to learn how to discover and exploit a Type Juggling Issue? It is barely possible without access to the source code. Active exploitation is a minor part of this course and is done manually without automation tools.

So if you do have programming skills already and are interested in strengthening your vulnerability discovery skills on source code review engagements, then this course might be the one for you. I have 5+ years of experience in auditing, primarily PHP and Java applications, and found this course to be challenging in many (but not all) chapters. However, this course still helped me sharpen my view on how small coding errors can result in impactful bugs by just leaving out a single equal sign.

But suppose you’ve never touched the initially mentioned bug classes, and you have also never touched on different programming languages and concepts such as object orientation. In that case, you should spend some time on practical programming first before buying this course.