API-specific attack: Understanding API injection and its effects

- August 07, 2025

In today's hypercontaneous digital landscape, application programming interfaces (APIs) are the backbone of modern web and mobile application. They enable spontaneous communication between various software systems, making everything convenient from login functional to payment processing. However, this increased dependence on API has introduced new attack vector-particularly API-specific attacks such as API injections, where the attackers manipulate API requests to obtain unauthorized access, remove sensitive information or disrupt the application argument.

This blog dives deeply into API injection attacks, discovering the best practices for their origin, general exploitation techniques, detection strategies, and mitigation.

📜 History and development of API attacks

APIs have existed since the early days of computing, but their explosive increase in the early 2000s has increased, which increases with the increasing requirement of APIs, SOAP, and cloud-based microservices. As the API became central for business operations, security researchers noticed that many were being applied without proper authentication, rate limiting, or input verification.

The concept of API injection stems from the broader code injection family, including SQL injections and command injections. However, API injection exploits API's programmatic interfaces and parameter-powered nature.

With more applications of the third-party API and with their own exposure, the attackers felt that manipulating input values can expose sensitive closing points, bypass authentication mechanisms, or unauthorized actions.

⚠ What is API injection?

The API refers to a section of the injection attacks where an API request to change the execution argument of the API is inserted as input. Depending on the absence of APIs's backend architecture and verification, it can have serious consequences, including:

Unauthorized data access
Account takeover
Remote code execution
Privilege escalation
Denial of service

Common examples of API injection include:

SQL Injection via API: Inserting SQL queries into parameters like userId=1 OR 1=1
Command Injection via API: Injecting shell commands in parameters processed by the server
XML Injection (in SOAP APIs): Manipulating XML payloads to gain backend access
Header Injection: Tampering with HTTP headers to inject harmful payloads
JWT Manipulation: Altering tokens passed through APIs for authentication

🧪 How API Injection Works: Step-by-Step

Let’s break down a typical API Injection attack through a real-world-inspired scenario:

Scenario:

An API endpoint https://example.com/api/getUser?id=123 is meant to return user details for the authenticated user.

Step 1: Reconnaissance

The attacker observes that the API doesn’t validate inputs thoroughly. They try altering the URL:

https://example.com/api/getUser?id=123 OR 1=1

If the API is vulnerable to SQL injection, this may result in the server executing a database query like:

sql
SELECT * FROM users WHERE id = 123 OR 1=1

This would return all user records, violating privacy and authorization controls.

Step 2: API Mapping

Using tools like Burp Suite, Postman, or OWASP ZAP, attackers identify other endpoints like:

/api/admin/deleteUser
/api/transactions/export

If access control is weak, they might inject administrative commands or data retrieval functions.

Step 3: Exploitation

Attackers send crafted payloads via:

JSON body parameters
URL query strings
Custom headers
Cookies

They might chain this with JWT manipulation or session hijacking to escalate the attack.

🧩 Common API Injection Techniques

1. SQL Injection

Used when backend queries don’t sanitize user input.

json
{
"username": "' OR 1=1 --",
"password": "irrelevant"
}

2. Command Injection

Injecting system commands:

json
{
"ping": "8.8.8.8 && rm -rf /"
}

3. LDAP Injection

Tampering with LDAP queries:

json
{
"user": "*)(&))"
}

4. NoSQL Injection

Targeting NoSQL databases like MongoDB:

json
{
"user": {"$ne": null}
}

5. GraphQL Injection

Manipulating GraphQL queries:

graphql
{
user(id: "123") {
password
creditCard
}
}

🔍 How to Detect API Injection Vulnerabilities

Detecting API-specific injection requires a combination of manual testing, automated tools, and runtime monitoring.

1. Static Code Analysis

Analyze API source code to find:

Direct user input in queries
Lack of input validation or encoding
Unsafe eval() or exec() functions

2. Dynamic Testing (DAST)

Use tools like:

OWASP ZAP
Burp Suite
Postman Fuzzer

These simulate API calls with malformed inputs to detect unexpected responses.

3. API Gateway Monitoring

Track anomalies in:

Rate of requests per user
Unusual HTTP methods (e.g., DELETE from non-admins)
JWT token tampering

4. Security Logging

Enable detailed logs for:

Request payloads
User activity
Error responses

Use SIEM tools to analyze suspicious patterns.

💥 How Attackers Exploit Vulnerable APIs

Attackers often follow these steps:

1. Information Gathering

They discover open API endpoints via:

Swagger docs (often left public)
Web/mobile app reverse engineering
DNS and subdomain brute forcing

2. Testing for Injection

They manipulate parameters in:

REST paths: /api/deleteUser/123
POST bodies: {"userId": "1 OR 1=1"}
Headers: X-User-Role: admin

3. Session Hijacking

If session tokens or API keys are improperly handled, attackers can impersonate legitimate users.

4. Privilege Escalation

They identify whether standard users can access admin functions by fuzzing endpoint parameters.

5. Data Exfiltration

They extract sensitive data such as:

PII (name, email, address)
Credentials
API keys and secrets

🛡️ How to Prevent API Injection Attacks

1. Input Validation & Sanitization

Accept only expected data types
Whitelist allowed characters
Use libraries to escape special characters

2. Parameterized Queries

Use prepared statements in SQL/NoSQL:

python
query = "SELECT * FROM users WHERE id = ?"
cursor.execute(query, (user_id,))

3. Authentication & Authorization

Use OAuth2, JWT, and proper token handling
Validate scopes and roles at every endpoint

4. Rate Limiting and Throttling

Prevent brute-force attacks by limiting requests per IP/token.

5. Use API Gateways

Gateways like AWS API Gateway, Kong, or Apigee can:

Monitor traffic
Enforce security policies
Perform WAF-level inspections

6. Secure Error Handling

Avoid exposing stack traces or backend info. Always return generic error messages for failed requests.

7. Logging and Monitoring

Track API activity and set up alerts for:

Repeated failed login attempts
Requests from suspicious IPs
Unexpected HTTP methods or payloads

📘 conclusion

API-specific attacks, especially API injections, are becoming increasingly prevalent as organizations adopt cloud composition and micro-class architecture. These attacks target the very interfaces that power modern applications and services. The openness and access of the API makes them both a powerful tool and a potential liability if not properly safe.

Through proper design, rigorous verification, strong authentication, and continuous monitoring, developers and security teams can build APIs that are flexible for injections and other sophisticated attacks.