API Code Review Service

Why API Code Review

APIs are the attack surface of modern applications. Every public endpoint is a potential entry point for attackers. Every internal service-to-service call is an opportunity for data leakage or privilege escalation.

Common API security problems:

• Authentication bypass allowing unauthorized access
• Authorization flaws exposing other users’ data
• Injection vulnerabilities from unvalidated input
• Information leakage through verbose responses
• Abuse potential from missing rate limits

API reviews identify these vulnerabilities before they’re exploited.

What Gets Reviewed

Authentication Security

How the API verifies identity:

Token Management

• JWT implementation and validation
• Token storage and transmission
• Token expiration and refresh
• Token revocation capability

API Key Security

• Key generation entropy
• Key transmission (headers vs. URLs)
• Key rotation capability
• Key scope and permissions

OAuth Implementation

• Flow implementation correctness
• State parameter usage
• Redirect URI validation
• Scope validation

Authorization Analysis

How the API controls access:

Object-Level Authorization

• User ownership verification
• IDOR vulnerability detection
• Resource access patterns
• Permission inheritance

Function-Level Authorization

• Admin endpoint protection
• Role-based access control
• Permission checking consistency
• Default-deny patterns

Data-Level Authorization

• Field-level access control
• Tenant data isolation
• Audit data protection
• Sensitive field handling

Input Validation

How the API handles user input:

Request Validation

• Schema validation implementation
• Type coercion safety
• Size limit enforcement
• Required field handling

Injection Prevention

• SQL query parameterization
• NoSQL operator handling
• Command injection prevention
• Template injection protection

File Handling

• Upload type validation
• File size limits
• Path traversal prevention
• Filename sanitization

Response Security

What the API reveals:

Data Exposure

• Excessive data in responses
• Internal ID exposure
• Stack traces in errors
• Debug information leakage

Error Handling

• Error message consistency
• Sensitive data in errors
• Timing attack prevention
• Error code standardization

Performance Analysis

API efficiency under load:

Query Efficiency

• N+1 queries in resolvers
• Unbounded result sets
• Missing pagination
• Query complexity limits

Resource Management

• Connection pooling
• Memory usage patterns
• Request timeout handling
• Background job offloading

Caching

• Response caching opportunities
• Cache-Control headers
• ETag implementation
• Cache invalidation

Design Quality

API design best practices:

REST Design

• Resource naming conventions
• HTTP method appropriateness
• Status code usage
• HATEOAS implementation

GraphQL Design

• Schema design patterns
• Resolver organization
• Query depth limiting
• Complexity analysis

Consistency

• Naming conventions
• Error format consistency
• Pagination patterns
• Versioning strategy

Common API Issues Found

Security Vulnerabilities

BOLA (Broken Object-Level Authorization) The most common API vulnerability:

• Resource IDs in URLs without ownership checks
• Assuming frontend filtering is sufficient
• Missing authorization middleware
• Inconsistent permission checking

Injection Attacks

• SQL injection in filter parameters
• NoSQL injection in MongoDB queries
• LDAP injection in search
• GraphQL query injection

Authentication Issues

• JWT signature not verified
• Token not checked on every request
• Password reset tokens too predictable
• API keys with excessive permissions

Performance Problems

Database Issues

• N+1 queries in GraphQL resolvers
• Missing indexes for common filters
• Full table scans on list endpoints
• No query result limits

Resource Exhaustion

• No request size limits
• Unbounded query complexity
• Missing pagination
• No rate limiting

Design Issues

Inconsistency

• Mixed naming conventions
• Varying error formats
• Inconsistent pagination
• Unclear versioning

Poor Error Handling

• Generic error messages
• Leaking internal details
• Missing error codes
• No retry guidance

API-Specific Analysis

REST APIs

• Resource hierarchy design
• HTTP semantics correctness
• Content negotiation
• Hypermedia implementation

GraphQL APIs

• Schema design quality
• Query complexity limits
• Resolver N+1 prevention
• Introspection security
• Subscription security

gRPC/Internal APIs

• Service definition quality
• Error handling patterns
• Streaming implementation
• Service mesh integration

Review Methodology

The API review follows a systematic approach:

1. Authentication Audit — Token handling, session management
2. Authorization Analysis — Object and function-level access
3. Input Validation Review — All endpoints, all input sources
4. Response Analysis — Data exposure, error handling
5. Performance Assessment — Efficiency under load
6. Design Evaluation — Consistency, best practices
7. Recommendations — Prioritized by risk and effort

The Review Report

You receive a comprehensive report including:

• Security Findings — Vulnerabilities with severity ratings
• Authorization Analysis — Access control gaps
• Performance Issues — Bottlenecks and optimizations
• Design Recommendations — Consistency and best practices
• Code Examples — Vulnerable code and secure alternatives
• Prioritized Roadmap — What to fix first

Getting Started

To begin an API code review, provide:

• Repository access
• API framework and language
• Authentication mechanism
• OpenAPI/GraphQL schema (if available)
• Specific concerns or focus areas

A quote will be provided within 24-48 hours based on API complexity.