It was 02:45 AM. The blue light from the screen illuminated a cold coffee stain on the desk while the blinking cursor on the terminal seemed to be mocking me. In the extensive penetration testing project we were running for example-corp, we hadn't found a single open door from the outside. The firewalls were acting like beasts, and the EDRs weren't letting a fly pass. Until that moment. A legacy test server—overlooked, forgotten, and probably not logged into for years—winked at me from a dark corner of the network. That’s when it hit me: Security isn't about your strongest link; it's about that weakest link you forgot existed.
Moving Beyond the Tools
There’s this common perception in the market when it comes to penetration testing: "Mate, we run Nmap, we fire up Nessus, then we just print the report." If that’s what you think, I’m sorry, but you're not even a candidate for a 'script kiddie,' let alone a cybersecurity expert. Real pentesting isn't just about knowing how a system works; it’s the art of imagining how it can be 'broken.'
When I reached that legacy server that night, it was running an old Jenkins instance. A standard scanner might have flagged it as 'medium risk' and moved on, but through the eyes of a Red Teamer, it was a gold mine. Why? Because the 'Script Console' feature in Jenkins, when combined with authorization misconfigurations, gives you the power to execute code directly on the system (RCE).
A Scenario: Breaching the System via Jenkins
Now, let's get into the kitchen. We'll go through a defanged example. Imagine you've gained access to the Jenkins script console. You can read the internal state of the system with a simple Groovy script like this:
// DEFANGED EXAMPLE
// Our goal is to understand our identity on the system
def command = "whoami"
def process = command.execute()
println process.text
If you see nt authority\system or root as the output, it’s game over. You’re no longer just touching a web app; you’re touching the heart of the operating system. But it doesn’t end there. Our goal isn’t to tear the system down, but to understand why it was left vulnerable in the first place.
Lateral Movement: Moving Silently Inside
We’re in. Now what? This is my favorite stage of a pentest: Lateral Movement. Compromising a single machine doesn't mean much; the real targets are Active Directory (AD) or database servers holding sensitive data.
In a penetration test, 'credential dumping' from the first compromised machine is critical. While the tools used to pull passwords or hashes from memory are quite advanced, modern EDR (Endpoint Detection and Response) solutions catch them instantly.
For instance, the moment you touch the lsass.exe process, alarm bells start ringing. So, what do we do? Instead of dumping the memory directly, we try more 'stealthy' methods.
# Defanged - Logic for memory dumping (Representative)
# In real life, EDR would catch this k...