Unsafe Consumption of APIs (OWASP 10): Securing Third-Party Integrations

Modern applications are built on connections, from payment gateways and address validators to data cleansing and analytics tools. While these third-party APIs make development faster and more flexible, they also introduce new attack surfaces outside your direct control.

The final principle in the OWASP API Security Top 10, Unsafe Consumption of APIs, addresses this very issue. It’s a reminder that an organization is only as secure as the APIs it chooses to consume.

Why Third-Party APIs are a Double-Edged Sword

Every modern digital ecosystem relies on external services. Financial apps connect to credit bureaus, retailers rely on shipping APIs, and healthcare systems pull records from data aggregators.

These connections bring efficiency and scale, but also risk. If a third-party API is compromised or poorly validated, attackers can slip through your defenses without ever touching your core infrastructure.

Unsafe consumption isn’t about your code being broken; it’s about trusting someone else’s code too much.

What is Unsafe Consumption of APIs?

Example: SwissBorg and Kiln – Third-Party API Exploit Leads to $41 Million Loss

What it means

Unsafe Consumption of APIs happens when an application blindly trusts an external API or service without verifying its security, responses, or access controls.
It’s not just about malformed data, it's about the inherent risk of depending on another company’s API for core business operations.

When your product relies on a third-party integration, you inherit that provider’s vulnerabilities. A flaw on their end can directly expose your environment, data, and customers.

What happened

SwissBorg, a popular crypto investment platform, partnered with a third-party service called Kiln to manage staking operations for its users’ Solana holdings.
In early 2025, attackers exploited a vulnerability in Kiln’s API SwissBorg’s integration partner gaining unauthorized access to the staking system.

Through this breach, attackers reassigned staked Solana and triggered unauthorized withdrawals, ultimately stealing 192,600 SOL, worth roughly $41 million.
Because the compromise happened on Kiln’s side, SwissBorg had no direct control over the exploit but its users were still affected. SwissBorg later reimbursed the losses from its own funds and Kiln exited the Ethereum validation business shortly after.

Why this matters

This is the core danger of Unsafe API Consumption (OWASP API10). Even if your own APIs are secure, your ecosystem isn’t one vulnerable partner that can compromise your entire platform.
It’s the same principle seen in other incidents, like Experian’s exposure of financial data through insecure integrations.

Lesson for developers

Third-party APIs are not “trusted by default.” Treat them as external inputs that require the same level of validation and oversight as user data.

How to protect your organization:

1. Vet third-party APIs before integration. Review their authentication, rate limits, and data handling practices.
2. Validate and sanitize all responses. Don’t assume external APIs always return safe or consistent data.
3. Monitor and log external API activity. Track anomalies, failed responses, and unexpected data patterns.
4. Encrypt and authenticate all third-party communications. Use TLS and signed requests to prevent interception or tampering.
5. Build fail-safes. If a third-party API misbehaves or becomes compromised, ensure your system can isolate or disable it without halting core functions.

In simple terms:

Unsafe API consumption is about trust without verification. You may not control your partners’ security but their mistakes can become your breach.

Read our blog on API Testing Automation to learn how continuous testing can identify integration risks before they impact production.

Real-World Example – The Address Verification Attack

The APIsec University transcript illustrates this risk through a clear scenario.
Imagine your app verifies user addresses through a third-party data cleansing API.

An attacker discovers which provider you’re using and injects malicious content into the third-party’s system. They then submit a loan application on your site with an address like:

123 Fake Street; DROP TABLE users;

When your application receives the response back, the command is executed as part of the address data. Suddenly, your database is at risk, not because your code was vulnerable, but because you trusted external data too much.

Another example involves redirects. If your third-party API redirects requests to new URLs, an attacker could modify that path to send users to a phishing or malware site.

The lesson: never trust data or commands originating from outside your control without validation.

Why Unsafe API Consumption Happens

Unsafe consumption isn’t born of laziness, it’s a side effect of speed and complexity. Common causes include:

• Rapid development cycles where security testing is skipped to meet deadlines.
• Assuming third-party APIs are secure because they’re popular or paid.
• Lack of schema validation for incoming responses.
• Over-trust in redirects or data transformation APIs.
• Missing audits of vendor security practices.
• No inventory of external integrations, so teams don’t know what’s connected.

Each of these creates a blind spot that attackers can exploit.

Common Vulnerabilities in Third-Party Integrations

Unsafe consumption often shows up as technical flaws such as:

1. Injection Attacks: Malicious inputs from third-party responses modify your database or logic.
2. Unvalidated Redirects: External APIs redirect users to untrusted URLs.
3. Cross-Site Scripting (XSS): Returned data includes script tags executed in the user’s browser.
4. Insecure Deserialization: Objects sent by third parties are reconstructed unsafely.
5. Weak Authentication or Encryption: Third-party APIs using HTTP or outdated TLS versions.

Even small integrations can open huge holes when these issues go unchecked.

OWASP API10 Risks and Business Impact

The consequences of unsafe API consumption extend beyond technical damage:

• Data Theft or Exposure: Unvalidated responses leak user or financial data.
• Reputation Loss: Customers blame you, not your third-party vendor.
• Regulatory Violations: Unsecure data flows violate GDPR or HIPAA.
• Supply Chain Compromise: A vulnerable partner infects multiple connected clients.
• Financial Loss: Breach response and downtime cost millions.

A single injected payload or redirect can turn a trusted integration into a breach headline.

Best Practices to Prevent Unsafe Consumption of APIs

Securing third-party consumption starts with a “trust but verify” mindset. Here’s how to apply it:

1. Validate Everything

• Enforce input/output schemas using OpenAPI specs.
• Reject unexpected fields or formats.

2. Sanitize Data

• Clean all external data before storing or processing.
• Block control characters and suspicious commands.

3. Audit Third-Party Vendors

• Review their security certifications and patch policies.
• Confirm they use TLS 1.2+, authentication, and rate limits.

4. Limit Redirects

• Allow redirects only to known domains under your control.

5. Monitor and Log API Traffic

• Track external calls for anomalies, response patterns, and error rates.

6. Maintain an API Inventory

• Know exactly which third-party APIs you’re using and why.

7. Automate Security Testing

• Integrate automated scanning to validate APIs continuously, not just during deployment.

How APIsec.ai Automates Third-Party API Security Testing

Managing dozens of external integrations manually is impossible. APIsec.ai solves this by automating API discovery, validation, and security testing across your entire ecosystem.

• Continuous Third-Party Discovery

APIsec.ai automatically maps all inbound and outbound API dependencies, including those linked to third parties or shadow integrations.

• AI-Driven Validation

Its AI engine tests real-world attack scenarios, like injection and redirect exploits, to see how your system responds to unsafe inputs.

• OWASP Compliance Coverage

The platform continuously tests against the OWASP API Top 10, including #10 – Unsafe Consumption of APIs, ensuring every integration meets best-practice security standards.

• CI/CD Pipeline Integration

Security checks run automatically as new APIs are added or updated, catching issues before production.

• Real-Time Reporting

Unified dashboards show exposure maps, validation results, and remediation steps so teams can respond fast.

APIsec.ai empowers organizations to trust their third-party integrations without blind faith because it validates every connection, every time.

Conclusion – Trust But Verify Your APIs

The final OWASP API Security Top 10 risk Unsafe Consumption of APIs, reminds us that security extends beyond our own code. Every external integration introduces a potential pathway for attackers.

Validating data, auditing vendors, and automating security testing are no longer optional, they’re foundational.

APIsec.ai helps teams stay ahead by detecting unsafe consumption patterns, testing API behavior continuously, and giving businesses the confidence to innovate securely.

Secure what you build and what you consume. Start a free API security assessment with APIsec.ai to see how your third-party connections really perform.

FAQs

1. What is Unsafe Consumption of APIs?

It refers to using external or third-party APIs without validating their responses or security, leading to data injection, redirects, or breaches.

2. Why was it added to the OWASP API Top 10?

Because most modern applications depend on third-party APIs, and many breaches now originate from insecure integrations outside a company’s control.

3. What are common examples of unsafe API consumption?

Injection attacks via data cleansing APIs, redirect abuse through external calls, and supply-chain breaches from vulnerable vendors.

4. How can organizations mitigate these risks?

By validating all third-party data, auditing vendors, limiting redirects, and using automated testing tools like APIsec.ai.

5. How does APIsec.ai help with OWASP API10 compliance?

It automates validation and OWASP testing for both internal and external APIs, ensuring continuous visibility and compliance.

6. What’s the most important rule for safe API consumption?

Never trust external data blindly, always validate and test what your APIs consume.

‍