Art of Chaining Security Vulnerabilities in Penetration testing

Web applications are rarely compromised through a single vulnerability alone. Instead, attackers often chain multiple seemingly low-impact issues—like XSS, CSRF, clickjacking, or open redirects—to execute complex, high-impact exploits. Understanding how these vulnerabilities interact is key to defending modern apps, especially those deployed in cloud environments. In this blog, we walk through real-world scenarios that demonstrate how chained vulnerabilities can escalate risk dramatically. If you're new to the subject, or want to brush up on the fundamentals, check out the OWASP Top 10 —a standard reference for the most critical web application security risks.

Scenario 1: Reflected Cross-Site Scripting (XSS)

Vulnerability: Reflected Cross-Site Scripting (XSS)

In this scenario, there's a web application where user inputs aren't properly sanitized before being reflected to the user. An attacker could craft a malicious link containing a script that executes when clicked by a victim.

Application Scenario

Imagine a basic web application where users can submit comments on a forum. When a user submits a comment, it's displayed back to them without proper sanitization, making it susceptible to XSS attacks.

HTTP Request Example

POST /submitComment HTTP/1.1
Host: example.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 53

comment=<script>alert('XSS attack!')</script>&submit=Submit

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Chaining with Another Vulnerability: Cross-Site Request Forgery (CSRF)

Vulnerability: Cross-Site Request Forgery (CSRF)

CSRF allows an attacker to perform actions on behalf of an authenticated user without their consent by exploiting the trust that a site has in the user's browser.

Application Scenario

The same web application is vulnerable to CSRF attacks, where actions can be triggered through forged requests.

HTTP Request Example (CSRF)

POST /changePassword HTTP/1.1
Host: example.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 69
Cookie: session=attacker_session_cookie

newPassword=evilpassword&confirmPassword=evilpassword&submit=Change+Password

Chained Attack Flow

1. The attacker lures the victim to visit a malicious web page.
2. The page executes JavaScript that sends a forged CSRF request to the vulnerable web app.
3. The same page may include an XSS payload that steals session cookies or performs actions as the victim.
4. The victim’s password is changed without their knowledge — account compromised.

Consequence

The combination of XSS and CSRF allows an attacker to hijack user sessions, change account credentials without the victim’s knowledge, and perform unauthorized actions—leading to full account compromise.

Scenario 2: Clickjacking

Low-Impact Security Issue: Clickjacking

Clickjacking tricks a user into clicking something different from what they perceive, potentially revealing confidential information or performing unintended actions.

Application Scenario

A social media platform allows users to upload images with captions but doesn’t implement clickjacking protection.

HTTP Request Example

POST /uploadImage HTTP/1.1
Host: example.com
Content-Type: multipart/form-data; boundary=---------------------------974767299852498929531610575
Content-Length: 554

-----------------------------974767299852498929531610575
Content-Disposition: form-data; name="image"; filename="example.jpg"
Content-Type: image/jpeg

(binary data)

-----------------------------974767299852498929531610575
Content-Disposition: form-data; name="caption"

Check out my latest pic!

-----------------------------974767299852498929531610575--

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Chaining with XSS Vulnerability

Application Scenario

The same platform is vulnerable to XSS due to improper validation in the caption field.

HTTP Request Example with XSS Payload

POST /uploadImage HTTP/1.1
Host: example.com
Content-Type: multipart/form-data; boundary=---------------------------974767299852498929531610575
Content-Length: 613

-----------------------------974767299852498929531610575
Content-Disposition: form-data; name="image"; filename="example.jpg"
Content-Type: image/jpeg

(binary data)

-----------------------------974767299852498929531610575
Content-Disposition: form-data; name="caption"

<script>alert('Your session has been hijacked!');</script>

-----------------------------974767299852498929531610575--

Chained Attack Flow

1. Clickjacking: The attacker overlays an invisible iframe over the upload button to trick users.
2. XSS: A script in the caption executes after upload, stealing cookies or performing unauthorized actions.

Consequence

The user unknowingly runs a malicious script while uploading an image, leading to session hijacking or worse.

Scenario 3: Open Redirect

Low-Impact Security Issue: Open Redirect

An open redirect vulnerability lets attackers redirect users to malicious sites through a trusted domain.

Application Scenario

A site offers redirection via URLs like /redirect?url=<external_url>.

HTTP Request Example

GET /redirect?url=https://malicious-site.com HTTP/1.1
Host: vulnerable-site.com

---

Chaining with Server-Side Request Forgery (SSRF)

SSRF Request Example

POST /api/endpoint HTTP/1.1
Host: vulnerable-site.com
Content-Type: application/json

{"url": "http://internal-service/vulnerable-endpoint"}

---

Chained Attack Flow

1. Attacker uses open redirect to redirect to an internal SSRF endpoint.
2. The redirection causes the server to make a request to internal services.
3. This can expose sensitive data or allow lateral movement within internal networks.

Consequence

By chaining Open Redirect with SSRF, an attacker can access internal systems, bypass network controls, and exploit internal APIs—demonstrating how "low-severity" issues can lead to serious security breaches.

Scenario 4: Insecure Deserialization

Vulnerability: Insecure Deserialization

Insecure deserialization occurs when untrusted or tampered data is deserialized by an application, allowing remote code execution or privilege escalation.

Application Scenario

A file-sharing application uses serialized objects to store user preferences. These objects are deserialized on the server without any validation.

HTTP Request Example

POST /updatePreferences HTTP/1.1
Host: example.com
Content-Type: application/x-java-serialized-object
Content-Length: 234

<malicious serialized Java object>

Chaining with Broken Access Control

Vulnerability: Broken Access Control

Once deserialization allows remote code execution, the attacker can escalate privileges due to insufficient access restrictions.

Application Scenario

The attacker runs a payload that changes their user role from “basic” to “admin” by modifying internal variables.

Chained Attack Flow

1. The attacker sends a tampered serialized object to the application.
2. The application deserializes it without validation, executing arbitrary code.
3. The attacker modifies their user role, bypassing access control.
4. Now with admin privileges, the attacker exfiltrates sensitive data or modifies system settings.

Consequence

Remote code execution plus privilege escalation leads to total application compromise.

Scenario 5: Directory Traversal

Vulnerability: Directory Traversal (Path Traversal)

Directory traversal allows attackers to access files and directories outside the intended file structure using sequences like ../../.

Application Scenario

A document viewer application lets users download reports by specifying filenames. It fails to sanitize file paths.

HTTP Request Example

GET /download?file=../../../../etc/passwd HTTP/1.1  
Host: example.com  

Chaining with Information Disclosure

Vulnerability: Sensitive Data Exposure

The attacker uses directory traversal to access configuration files containing credentials, API keys, or internal endpoints.

Chained Attack Flow

1. The attacker exploits directory traversal to read restricted server files.
2. Among the accessed files is a .env file or config file with database credentials.
3. The attacker uses this information to authenticate into the backend or cloud services.
4. Database and system compromise follows.

Consequence

Sensitive internal files are exposed, and chaining this with credential harvesting enables deeper infiltration.

Securing the Gaps: Lessons from Chained Web Attacks

While individual vulnerabilities like XSS, CSRF, clickjacking, or open redirects may seem minor in isolation, attackers often exploit them in combination to achieve far more damaging outcomes. As shown in the above examples, it is possible to chain together several low-impact flaws to create account takeovers, session hijacking, internal system compromise, and data leakage. This layered exploitation strategy highlights the importance of not underestimating seemingly insignificant bugs.

For developers and security teams, it's essential to take a comprehensive approach to web application security—periodic code auditing, using layered defenses (such as input validation, CSRF tokens, and Content Security Policy), and keeping up to date with popular vulnerabilities through means such as the OWASP Top 10. In cloud environments where app components and APIs are highly dispersed, the threat is even greater. Proactive detection, timely patching, and a security-first mindset in development can prevent attackers from discovering and chaining these weak links. Simply put, the real threat is not in the isolated faults themselves, but in how they collaborate.