Art of Chaining Security Vulnerabilities in Penetration testing

Ever wondered how minor bugs turn into full system takeovers? Attackers rarely rely on a single flaw—they chain multiple low-impact issues, like XSS, CSRF, clickjacking, open redirects, or insecure deserialization, to pull off high-impact exploits. Each vulnerability might seem harmless on its own, but together they can compromise accounts, steal sensitive data, or even take control of backend systems.

Modern web applications—especially cloud-based ones—connect APIs, microservices, and user interfaces, creating a web of attack surfaces. A small, overlooked gap in a seemingly isolated component can quickly cascade into a full compromise. Understanding how vulnerabilities interact is no longer optional; it’s critical for securing your apps.

In this blog, we walk through seven real-world scenarios that reveal the art of chaining vulnerabilities. From seemingly minor bugs to major breaches, you’ll see how attackers escalate risk step by step. For reference, check out the OWASP Top 10, the standard for critical web application security risks.

The real danger isn’t each bug alone—it’s how attackers chain them. Let’s explore the scenarios.

Scenario 1: Reflected Cross-Site Scripting (XSS)

Cross-Site Scripting may look like a harmless text injection—but it’s often the first domino to fall. When an attacker sneaks malicious JavaScript into a trusted web page, every visitor becomes a potential target, and their session tokens a prize.

Low-Impact Security Issue: 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 

Chaining with 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

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

A social media platform allows users to upload images with captions but doesn’t implement clickjacking protection. An attacker can overlay an invisible iframe over the upload button, tricking users into executing actions they didn’t intend.

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--

Chaining with XSS

Vulnerability: Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS) occurs when user-supplied data is rendered in a page without proper encoding or sanitization, allowing an attacker to inject JavaScript that runs in other users’ browsers and can steal session tokens, perform actions, or load remote payloads.

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

When an application blindly trusts serialized objects from users, it’s like letting strangers rewrite parts of your codebase. Insecure deserialization opens a path for attackers to manipulate logic, inject payloads, and execute arbitrary commands on the server.

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 SSRF

Vulnerability: Server-Side Request Forgery (SSRF)

SSRF occurs when a server-side component fetches attacker-controlled URLs and performs requests on behalf of the attacker. An attacker can abuse this to reach internal-only services (internal APIs, cloud metadata endpoints, admin consoles) that are not directly accessible from the internet.

Application Scenario

The open-redirect is abused to point to an internal service URL; when the application follows that URL server-side (for validation, proxying, or previewing), it triggers internal requests. This lets the attacker probe internal endpoints, retrieve sensitive responses, or chain to further attacks (for example, metadata/credential theft).

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

CSRF attacks take advantage of trust—specifically, a user’s authenticated session. By embedding malicious requests into legitimate pages, attackers can trick users into transferring funds, changing settings, or deleting accounts without realizing they ever triggered the action.

Low-Impact Security Issue: 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.

HTTP Request Example

POST /updatePreferences HTTP/1.1 
Host: example.com 
Content-Type: application/x-java-serialized-object
Content-Length: 312
Cookie: session=victim_session_cookie

<serialized object>
  (java serialized payload that, when deserialized, sets user.role = "admin" 
   or invokes application logic to update role fields)  
</serialized object>`  

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

Directory traversal exploits a simple oversight in path handling. By inserting relative path sequences like ../, attackers can move outside permitted folders and access sensitive files—configurations, logs, or even password hashes—never meant to be exposed to the public.

Low-Impact Security Issue: Directory 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 Sensitive Data Exposure

Vulnerability: Sensitive Data Exposure

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

Application Scenario

The attacker exploits the download parameter to traverse out of the intended reports directory and read sensitive files. By requesting configuration files like .env or config.yml, they can harvest database credentials, API keys, or internal endpoints that enable further compromise (database access, cloud credential reuse, or lateral movement).

HTTP Request Example

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

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.

Scenario 6: Server-Side Request Forgery (SSRF)

In cloud environments, SSRF bugs can be deceptively dangerous. By tricking the server into sending requests to internal endpoints, attackers can reach sensitive cloud metadata services, exposing temporary IAM credentials that can be used to compromise storage, compute, and other cloud resources.

Low-Impact Security Issue: Server-Side Request Forgery (SSRF)

SSRF lets an attacker induce the server to make HTTP requests to arbitrary URLs. In cloud-hosted apps that call out to external resources, SSRF can become a direct path to internal-only endpoints—like cloud metadata services that hold temporary credentials.

Application Scenario

A microservice accepts a URL from users and fetches that URL server-side (e.g., to validate a webhook or preview remote content) without restricting allowed destinations.

SSRF Request Example

POST /fetchPreview HTTP/1.1 
Host: example.com
Content-Type: application/json

{"url":"http://169.254.169.254/latest/meta-data/iam/security-credentials/"} 

(On AWS, the metadata endpoint http://169.254.169.254 returns instance metadata including temporary IAM role credentials if the instance has an attached role.)

Chaining with Sensitive Data Exposure

Vulnerability: Sensitive Data Exposure

SSRF can expose cloud metadata endpoints, letting attackers steal temporary IAM credentials and gain unauthorized access to cloud resources.

Application Scenario

The application runs on a cloud VM/container with an attached IAM role that grants access to sensitive resources (S3, databases, secret stores). The SSRF allows the attacker to query the instance metadata endpoint and retrieve temporary credentials.

HTTP Request Example to retrieve credentials via SSRF

POST /fetchPreview HTTP/1.1 
Host: example.com
Content-Type: application/json

{"url":"http://169.254.169.254/latest/meta-data/iam/security-credentials/my-app-role"} 

Chained Attack Flow

1. Attacker finds the SSRF endpoint and crafts a request targeting the cloud metadata service.
2. Server fetches the metadata and returns IAM role credentials (access key, secret, token) to the attacker.
3. Attacker uses those credentials to call cloud APIs directly (S3, IAM, compute) from their own host.
4. With cloud API access, attacker lists and downloads sensitive buckets, creates additional compute instances, or escalates access by modifying IAM policies.

Consequence

A seemingly low-impact SSRF escalates into full cloud account compromise: exfiltration of sensitive data, creation of persistent backdoors, and lateral movement across cloud services. Because stolen credentials are valid for the cloud provider’s APIs, impact can be catastrophic.

Scenario 7: Broken Authentication

Weak authentication and missing rate limits may seem minor, but they invite large-scale automated abuse. Attackers combine leaked credentials with unprotected account-management flows to turn credential lists into real account takeovers.

Low-Impact Security Issue: Missing/Weak Rate Limiting on Auth Endpoints

APIs and login pages that don’t throttle or block repeated failed attempts allow credential stuffing at scale. Without progressive delays, account lockouts, or anomaly detection, attackers can try thousands of credential pairs quickly.

Application Scenario

A web app exposes POST /api/login that accepts JSON credentials and responds identically for success/failure. There’s no rate limiting, no progressive delays, and no account lockouts. The app also exposes POST /api/change-email which accepts a userId and newEmail but doesn’t require re‑authentication or ownership verification.

HTTP Request Example (login)

POST /api/login HTTP/1.1 
Host: example.com
Content-Type: application/json

{"username":"[email protected]","password":"P@ssw0rd123"} 

HTTP Request Example (change email - vulnerable)

POST /api/change-email HTTP/1.1  
Host: example.com
Content-Type: application/json 
Authorization: Bearer <attacker_token_or_omitted_ifUnauthenticated>

{"userId":"12345","newEmail":"[email protected]"} 

Chaining with Account Takeover

Vulnerability: Broken Authentication / IDOR

Endpoints that allow sensitive changes without re‑auth or that accept user-controlled IDs (IDOR) let attackers hijack account recovery flows after gaining entry.

Application Scenario

An attacker uses a botnet or proxy pool to perform credential stuffing against the login API. On finding valid credentials (or by abusing the unauthenticated userId parameter), they change the account’s recovery email to one they control.

HTTP Request Example (trigger password reset after email change)

POST /api/request-password-reset HTTP/1.1 
Host: example.com
Content-Type: application/json

{"email":"[email protected]"} 

Chained Attack Flow

1. Run credential stuffing (automated login attempts) to find valid credentials.
2. Log in and change the account email via the weak change-email endpoint (or abuse IDOR).
3. Trigger a password reset; the reset link is sent to the attacker-controlled email.
4. Complete the password reset and take over the account, then escalate privileges or exfiltrate data.

Consequence

Broken authentication and poorly protected account-management endpoints let attackers convert leaked credentials into real account takeovers quickly. Compromised accounts can be used for fraud, data theft, privilege escalation, or as footholds for broader attacks.

Securing the Gaps: Lessons from Chained Web Attacks

Minor web vulnerabilities—XSS here, CSRF there, a clickjacking trick, or an open redirect—often seem insignificant. But attackers don’t see them as isolated issues. They look for ways to chain these small flaws into high-impact attacks, turning low-severity bugs into account takeovers, session hijacking, data breaches, or full system compromise. The examples above show how quickly a few overlooked vulnerabilities can escalate into serious breaches.

For developers and security teams, the takeaway is simple: treat vulnerabilities as part of a larger system. Regular code audits, layered defenses like input validation, CSRF tokens, and Content Security Policy, and staying updated on the OWASP Top 10 are essential practices. A single fix isn’t enough—security must be proactive, not reactive.

In cloud environments, where applications and APIs are complex and distributed, minor gaps can cascade rapidly. Spotting, patching, and hardening weak links before attackers exploit them is crucial. The threat isn’t in isolated bugs—it’s in how attackers connect them to amplify impact.