Roughly 80% of documented cloud intrusions in 2025 trace back to vulnerabilities, exposed secrets, and misconfigurations, according to Wiz's analysis of publicly documented cloud incidents. APIs sit at the center of that exposure. They've become the primary attack surface in cloud environments, and traditional perimeter defenses were never built to see them.
Real API risk combines three things: an exposed endpoint, an identity with broad permissions, and sensitive data sitting behind it. A misconfiguration that touches none of those is low priority. One that touches all three is a breach.
Understanding how to secure your APIs starts with knowing what API security actually covers, why it matters, and where the most common gaps tend to hide.
What is API security?
API security is the practice of protecting application programming interfaces (APIs) from threats throughout their entire lifecycle. This means implementing authentication, authorization, encryption, and monitoring controls to prevent unauthorized access and data exposure. APIs face threats from external attackers and from internal misconfigurations, so security controls matter at every stage from design through deprecation.
APIs sit at the intersection of application, information, and network security. Unlike traditional web applications, APIs expose business logic and data pathways directly, which means a single weak endpoint can compromise multiple systems. General web application security focuses on the user-facing layer, things like session handling, cross-site scripting, and browser-based attacks. API security extends that focus to the machine-to-machine layer, where every endpoint is effectively a programmatic door into your data and your backend logic.
Effective API security addresses several interconnected concerns.
Access control ensures only authorized users and systems can reach specific endpoints.
Content validation verifies that incoming requests conform to expected formats and rejects malicious payloads.
Rate limiting prevents abuse by capping request volume per client.
Monitoring detects anomalies and unauthorized access attempts in real time.
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Why API security is more important than ever
APIs have become the primary attack vector in modern applications because they expose business logic and data pathways that traditional perimeter defenses cannot protect. When an attacker compromises an API, the blast radius extends well beyond a single application, and how far it extends depends on what that API can reach.
The business consequences are severe. In January 2024, an exposed REST API endpoint at Trello allowed unauthenticated users to query account information using email addresses, and attackers scraped roughly 15 million user profiles as a result. The endpoint itself wasn't catastrophic on its own. What made it dangerous was that it was internet-facing, required no authentication, and returned enough identity data to fuel phishing and account takeover campaigns. Without proper controls, organizations face data theft, system compromise, and regulatory violations that can take months to remediate.
Effective API security preserves data confidentiality, ensures authorized-only access, and maintains data integrity throughout transmission and storage. But the severity of any individual API risk scales with context. An endpoint with a minor flaw that sits behind strict authorization and touches no sensitive data is a low priority. The same flaw on a public endpoint tied to a privileged identity and a customer database is a different problem entirely, and this is the lens worth applying to every risk in the next section.
OWASP API security: Top 10 risks
The OWASP API Security Top 10 is the industry's shared baseline for understanding where API risk concentrates. We cover this list in full depth on our OWASP API Security page; here's the quick version.
1. Broken object level authorization
BOLA happens when an API doesn't verify a user has permission to access a specific object, letting attackers swap IDs in requests to reach other users' data. CVE-2024-1313, a 2024 BOLA flaw in Grafana, shows this risk persists even in actively maintained platforms.
2. Broken authentication
Weak or missing authentication gives attackers a direct path into an API. The Trello breach is the clearest example: a REST endpoint with no authentication let attackers query account data just by submitting email addresses.
3. Broken object property level authorization
APIs sometimes return more fields than necessary, or accept fields they shouldn't, assuming only authenticated users with the right context will call them. This covers what OWASP used to call excessive data exposure and mass assignment.
4. Unrestricted resource consumption
Without rate limiting, attackers can flood an API with requests and cause denial-of-service conditions. In cloud environments, this also drives runaway infrastructure costs before anyone notices the abuse.
5. Broken function level authorization
When function-level checks are missing or inconsistent, attackers can reach admin functions through endpoints never meant for them, often just by changing the HTTP method or path on a request they're already authorized to make.
6. Unrestricted access to sensitive business flows
Exposing a legitimate business process (account creation, ticket purchasing, fund transfers) without limits on frequency lets attackers automate abuse at scale for fraud or denial of service, even with no traditional vulnerability present.
7. Server-side request forgery (SSRF)
SSRF occurs when an API fetches a user-supplied URL without validating it, letting attackers reach internal resources. In the cloud, this is especially dangerous since attackers can target metadata services to steal credentials and escalate access.
8. Security misconfiguration
Missing patches, outdated systems, overly permissive CORS settings, and verbose error messages all expose sensitive data and open unauthorized access paths.
9. Improper inventory management
APIs expose far more endpoints than typical web apps. Poor documentation means old versions, debug endpoints, and undocumented integrations stay reachable long after anyone maintains them, creating shadow exposure attackers actively look for.
10. Unsafe consumption of APIs
Developers often trust third-party API responses without validating them, assuming well-known companies are inherently secure. That trust gap lets attackers exploit a compromised or manipulated integration and flow the attack straight into your systems.
By understanding these risks and applying proper controls at each stage, organizations can significantly reduce the threats associated with APIs. Visit OWASP's API Security Top 10 for a detailed breakdown of each risk.
API security for SOAP, REST, and GraphQL
Each of the three primary API architectures, SOAP, REST, and GraphQL, carries its own security implications.
| API Architecture | Data format/transport | Security implications |
|---|---|---|
| SOAP API security | XML-based messaging over HTTP, SMTP, and other protocols | Relies on transport-layer security (HTTPS) plus message-level security like XML digital signatures. WS-ReliableMessaging adds error-handling support, but the added complexity means misconfiguration is easy. |
| REST API security | JSON over HTTP/HTTPS | No built-in security; entirely dependent on implementation. Security comes down to HTTPS and token-based authentication (JWT) to verify caller identity and protect data in transit. |
| GraphQL API security | Strictly typed query language and runtime, typically over HTTPS | A single endpoint exposes the entire data graph. Unfiltered or deeply nested queries can overwhelm a server or leak excess data. Query depth limits, cost analysis, and throttling are essential, especially as GraphQL increasingly serves AI agents and orchestration tools. |
If your organization builds applications powered by generative AI or autonomous agents, the APIs behind those features face the same architectural risks described above, often at a larger scale. Learn more about the AI difference.
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API security risks in AI-powered applications
AI and large language model applications multiply the number of APIs an organization exposes, often faster than security teams can track them. Each new model, agent, or integration tends to bring its own set of endpoints, and many of these carry far more sensitive context than a typical CRUD API.
Model and inference endpoints expose your AI's core logic and outputs directly. These endpoints often accept unstructured input and can be probed for prompt injection, data leakage, or denial-of-service through resource-intensive queries.
Agent tooling and function calling extend an AI system's reach into real systems. When an agent can call internal APIs to take actions, like querying a database, sending an email, or modifying records, every one of those underlying APIs inherits the agent's permissions and becomes part of the attack surface.
Connected data stores and retrieval systems give AI applications access to sensitive data at scale. Retrieval-augmented generation pipelines often connect to APIs fronting customer data, internal documentation, or proprietary code, and a flaw in any of those APIs can expose that data through the AI application itself.
Third-party and shadow AI APIs are often adopted faster than they're inventoried. Teams frequently connect to external model providers, AI platforms, or plugins without formal review, creating undocumented integrations that carry the same risks as any other shadow API, plus the added concern of what data gets sent to a third party.
This is why the endpoint-plus-identity-plus-data lens matters most for AI applications. That combination — exposed model API, broad permissions, connected database — is a single toxic combination, and it's often the highest-severity risk in the entire environment.
10 API security best practices
Securing APIs effectively means layering controls across design, build, and runtime, so no single gap becomes a path to a breach. These ten practices build on each other, moving from knowing what you have to actively defending it in production.
1. Discover and inventory all APIs
Shadow APIs create dangerous blind spots that attackers actively exploit. These undocumented endpoints typically lack security controls entirely, and you can't secure what you don't know exists. That makes automated discovery the foundation of any API security program, scanning continuously for endpoints, parameters, and third-party integrations.
2. Identify API risks and vulnerabilities
Systematically evaluate APIs for vulnerabilities across their lifecycle, using automated scanners alongside penetration testing to catch configuration flaws, code weaknesses, and dependency issues. Assess against the OWASP risks above, including broken authentication, and give third-party APIs extra scrutiny since developers tend to trust that data more than user input.
3. Encrypt data in transit and at rest
Encrypt all data in transit with TLS 1.2 or higher, and encrypt sensitive fields within responses for defense in depth. Avoid outdated protocols like TLS 1.0 and 1.1, rotate keys regularly, and store encryption keys separately from the data they protect.
4. Implement strong authentication and authorization
Authentication verifies identity, often via OAuth 2.0 tokens, while authorization controls permissions through RBAC or attribute-based access control (ABAC). Regularly audit access controls, rotate API keys and tokens, and require multi-factor authentication for sensitive operations.
5. Use rate limits and throttling
Rate limiting caps how many calls a client can make in a set timeframe, protecting against DoS and DDoS attacks, while throttling slows excessive requests before they overwhelm the system. Customize limits by user role or client, and adjust thresholds based on usage patterns.
6. Use an API gateway
An API gateway centralizes authentication, input validation, rate limiting, and request routing, often integrating with a WAF against injection attacks. A gateway alone isn't enough though: it needs proper configuration, continuous monitoring, and visibility into what happens at the application layer beyond it.
7. Validate all input data
Input validation ensures APIs only accept data matching predefined formats, rejecting malformed input before it triggers injection attacks or buffer overflows. Apply validation across query parameters, headers, and payloads, and use strict schemas like JSON Schema to enforce rules at every endpoint.
8. Monitor and log API activity
Monitoring surfaces unauthorized access attempts and unusual request patterns, while centralized logging with timestamps, user identifiers, and IP addresses speeds up incident response. Automated alerts for anomalies like traffic spikes or repeated failed logins help refine your defenses over time.
9. Restrict data exposure
APIs should return only the fields a request needs, avoiding sensitive data in default responses through filtering and masking. Regularly review responses for privacy compliance, and restrict error messages so they don't leak implementation details.
10. Update and patch regularly
Apply security patches as soon as vulnerabilities are disclosed, using automated tools to track and deploy them without delay. Test patches in staging first to confirm compatibility before they reach production.
Key API security testing approaches
A strong API testing strategy covers design, build, and runtime, catching vulnerabilities where they're cheapest to fix.
Penetration testing
Manual testing catches what automated scanners miss, especially business logic flaws and authorization bypasses. Testing across unauthenticated, low-privilege, and administrative access contexts helps identify authorization gaps across user roles, and it's especially valuable for public-facing APIs and those handling sensitive data.
Fuzz testing
Fuzz testing sends unexpected, malformed, or random inputs to reveal how an API handles abnormal data without crashing or leaking information. Focus it on exposed endpoints, query parameters, and headers for the most value, and automate it for continuous coverage.
Automated vulnerability scanning
Automated scanning catches common flaws like misconfigurations, broken authentication, and injection vulnerabilities, ideally integrated into your development pipeline to catch issues before APIs go live. It doesn't replace manual testing, but adds continuous coverage that complements it.
Integrating security testing into CI/CD pipelines
Embedding these methods into CI/CD makes security a natural part of development: automated scans run with each build, while periodic penetration and fuzz tests validate security before release. This surfaces vulnerabilities during development, not after deployment.
How Wiz helps secure APIs from code to cloud
Traditional API security tools rely on agents or network scanners that create deployment complexity and leave visibility gaps. Wiz API Security Posture Management (API-SPM) takes a different approach, combining API security with cloud context in a single platform.
The Wiz Dynamic Scanner uses agentless scanning across major cloud providers to analyze every layer of your deployment. This reveals which APIs are exposed to the internet, what data they can access, and what permissions they hold. Wiz maps API risks alongside cloud resources, data sensitivity, and external exposure, surfacing toxic combinations that represent real attack paths rather than isolated vulnerabilities.
Wiz API-SPM continuously discovers and inventories managed, unmanaged, shadow, and zombie APIs, then assesses each one with exposure, identity, and data context. It automatically prioritizes the endpoints that create real risk, including APIs tied to AI-powered applications and the sensitive data or cloud permissions behind them.
This is the endpoint-plus-identity-plus-data approach in practice: instead of a long list of disconnected findings, you see which exposed APIs actually create a path to your sensitive data, and you can focus remediation there first.
If you want to go deeper on hardening your APIs, the API Security Best Practices Cheat Sheet covers proven, advanced techniques for securing your API infrastructure across its lifecycle. Or, try the free Wiz demo to see best practices in action.
FAQs for API security
Here are answers to some common questions about API security.