APIs power the digital world, connecting systems and enabling seamless communication between applications. From booking rides to processing payments, APIs make it all possible — but that connectivity also expands the attack surface, making API security a critical priority for technology-driven organizations.
APIs act as gatekeepers for everything from social logins to complex financial transactions. When left unsecured, they don’t just expose data — they can create pathways for fraud, unauthorized access to sensitive records, or disruption of business operations. That is why API-focused assessments are often considered alongside broader security practices, such as website penetration testing, infrastructure reviews, and application security testing, rather than treated as an isolated concern.
Why does API security matter?
API security is not optional. As more services and data are exposed through APIs, the risks continue to grow. Attackers can exploit poorly secured APIs to steal data, commit fraud, or cause operational disruption. Security must be built into the development process from day one — not treated as an afterthought.
What are APIs and how do they work?
An API (Application Programming Interface) is a contract between two systems that defines how they communicate, allowing applications to request and exchange data seamlessly. A few everyday examples:
- Ride booking: Google communicates with Lyft’s API to retrieve fare information and available vehicles.
- Payment processing: When you send money via Venmo, an API facilitates communication between the app and your bank to authenticate the transaction.
- Airfare aggregation: Platforms like Kayak use APIs to pull data from multiple airlines, presenting users with flight options and prices.
APIs also support microservices architecture, where different parts of a system — authentication, payment processing, data retrieval — communicate internally via APIs, each operating independently while sharing critical data.
The growth and prevalence of APIs
API adoption has grown exponentially. Akamai reported that 80% of all web traffic on their networks was API traffic. As more APIs are developed, security risks grow in parallel. Organizations maturing their security practices layer in best practices such as continuous testing, least-privilege access, and strong observability — starting with core concepts like endpoints, authentication, and tokens.
The security risks of APIs
APIs are a prime target for attackers due to their direct access to sensitive data and backend systems. Key risks include:
- Over-permissioned APIs: Excessive access rights allow attackers to retrieve more data or perform more actions than intended.
- Logic flaws: Vulnerabilities like Broken Object Level Authorization (BOLA) allow attackers to access unauthorized data.
- Exposed endpoints: Poorly secured APIs expose access points that are easy to exploit.
Unlike phishing or malware, API exploits often require only a few steps — making them faster and simpler to execute.
Real-world API breaches
These high-profile breaches illustrate why API security is critical:
- Experian: An unsecured API exposed the credit records of millions of Americans.
- Bumble: An API vulnerability leaked data on 100 million users.
- LinkedIn: Over 700 million user profiles were scraped due to API vulnerabilities.
- Venmo: APIs exposed 200 million transactions, including personal and payment data.
Beyond data loss, these breaches caused lasting damage to consumer trust and significant financial consequences.
API security and regulatory compliance
As API use has grown, so have regulatory requirements. Key compliance standards include:
- Financial regulations (FinCEN, open banking, PCI DSS): Mandate secure handling of financial transactions via APIs.
- Healthcare privacy laws (HIPAA, Cures Act): Require APIs to protect sensitive health data while maintaining accessibility.
- General privacy regulations (GDPR, CCPA): Govern how personal data is transmitted and processed through APIs.
API security must balance data protection with the accessibility needed for interoperability. As organizations increasingly expose large language model (LLM) endpoints, understanding risks like prompt injection also becomes an important part of a comprehensive API security strategy.
The challenges of securing APIs
Securing APIs isn’t straightforward. There are three key challenges to consider:
- Stopping unauthorized access: APIs must be protected against vulnerabilities that could let the wrong people in.
- Keeping sensitive data safe: APIs must handle health and financial data in line with privacy laws.
- Staying accessible: APIs need to work smoothly across organizations, partners, and customers — without cutting corners on security.
Getting this balance right is key to keeping your APIs secure and compliant.