API Security: Threats, Tools, and Best Practices

Breaches happen when APIs expose data without adequate protection measures like authentication, authorization, and encryption. The repercussions can range from data theft to complete system control, highlighting the need for rigorous API security measures.

Inadequately secured APIs can lead to devastating consequences, including financial losses and loss of consumer trust. Attackers might access customer data, financial records, or proprietary intellectual property, putting organizations at risk of compliance violations and legal penalties. 

The Impact of API Security Breaches 

If left unchecked, API security breaches can have significant impacts on organizations.

Data Theft and Exposure

APIs often handle sensitive data, such as personal information, financial records, and proprietary business data. When an API security breach occurs, attackers can extract this information, leading to significant privacy violations and financial losses. Data exposure can happen due to misconfigured APIs, weak authentication, or inadequate encryption. 

For example, if an API does not properly enforce access controls, unauthorized users may access confidential data. Additionally, exposed API keys or tokens can allow attackers to retrieve information without proper validation. Once stolen, the data may be sold on the dark web, used for identity theft, or leveraged in further attacks. 

Unauthorized Access

Unauthorized access occurs when attackers exploit weak authentication or authorization mechanisms to gain entry into an API. This can lead to data leaks, system manipulation, or unauthorized transactions. APIs that lack strong authentication, such as multi-factor authentication (MFA), are particularly vulnerable. 

Attackers can use credential stuffing, brute-force attacks, or stolen API keys to impersonate legitimate users. Weak authorization controls further compound the issue, allowing unauthorized users to perform actions beyond their intended permissions.

Service Disruption

Attackers can exploit APIs to disrupt services, rendering applications unusable or significantly degraded in performance. One common method is a denial-of-service (DoS) attack, where an API is overwhelmed with excessive requests, exhausting system resources.

Additionally, attackers may manipulate API endpoints to trigger unexpected system behaviors, leading to crashes or service outages. Poorly optimized rate limits and inadequate traffic monitoring can make APIs more susceptible to such attacks.

Reputational Damage

A security breach can severely damage an organization's reputation, eroding customer trust and confidence. When sensitive data is compromised or services are disrupted, users may perceive the organization as unreliable or incapable of protecting their information.

Negative publicity following an API breach can lead to customer attrition, reduced revenue, and difficulty acquiring new business. Public perception worsens when organizations fail to respond transparently or address security concerns promptly.

Legal and Compliance Issues

API breaches can result in severe legal and regulatory consequences, especially when they involve sensitive data subject to compliance frameworks such as GDPR, HIPAA, or PCI-DSS. Organizations may face hefty fines, lawsuits, and restrictions on operations if they fail to meet security requirements.

Non-compliance can lead to financial penalties and potential legal actions from affected customers or regulatory bodies. Additionally, organizations may be required to publicly disclose breaches, further damaging their credibility.

Common Causes of API Security Breaches 

Here are some of the main factors that result in vulnerable APIs.

Poor Authentication and Authorization

Without strong authentication, it's easy for attackers to masquerade as legitimate users, gaining unauthorized access to the system. Weak authorization practices further exacerbate this issue by allowing users to perform unauthorized actions within the system, potentially leading to data manipulation or leakage. 

Improper implementation of OAuth or similar protocols often leads to insecure token management. If tokens are easily replicable or do not expire after a session, attackers can exploit them to maintain persistent access to API resources. It is vital to routinely assess and update authentication and authorization practices to mitigate potential vulnerabilities.

Lack of Input Validation

Without rigorous input validation, APIs can be vulnerable to injection attacks, such as SQL injection, where malicious data is designed to manipulate database queries. Validating input ensures that only acceptable and expected data enters the system, reducing the likelihood of harmful data exploiting vulnerabilities.

Insufficient validation can lead APIs to expose internal system details, aiding attackers. Proper sanitization of input data is crucial in eliminating potential risks, ensuring endpoints only process validated and expected data. 

Overprivileged API Endpoints

Overprivileged API endpoints provide users with more permissions than necessary. When endpoints have extensive access rights, they expose more system functions to potential abuse or exploitation. Attackers can exploit these overprivileged endpoints to gain unauthorized access to sensitive data or manipulate critical operations.

Properly configured access controls ensure users and endpoints access only what is necessary, based on least privilege principles. Regular audits of API permissions help identify and rectify overprivileged endpoints, minimizing the attack surface.

Insufficient Logging and Monitoring

Insufficient logging and monitoring can obscure the visibility of potential security incidents, allowing breaches to go undetected. Comprehensive logging captures API interactions, enabling organizations to detect and respond to malicious activities promptly. 

Logs must be rich enough to support post-incident analysis, providing insights into breach causes and helping improve API security strategies. Continuous oversight is essential for maintaining a strong API security framework, mitigating risks, and ensuring compliance with industry standards.

Misconfigured APIs

Misconfigured APIs pose risks by inadvertently exposing sensitive data or functions to unauthorized users. Common misconfigurations include enabling default settings, not enforcing TLS encryption, and neglecting to restrict IP access. 

These errors can allow attackers easy entry points, making it essential to conduct regular configuration audits to decouple sensitive data and endpoints from unauthorized access. Effective configuration management involves defining secure defaults, managing environment variables appropriately, and reviewing endpoint exposure settings. 

Related content: Read our guide to API attacks

Tzvika Shneider

CEO, Pynt

Tzvika Shneider is a 20-year software security industry leader with a robust background in product and software management.

Tips from the expert

In my experience, here are tips that can help you better protect APIs and avoid security breaches:
• Implement token expiration with proper refresh mechanisms: Ensure that access tokens have short lifetimes and refresh tokens are securely managed. This minimizes the risk of long-term token abuse in case of a compromise. Rotate and revoke tokens dynamically to maintain control.
• Conduct continuous fuzz testing: Go beyond input validation by applying fuzz testing—automatically generating random, malformed, or unexpected inputs to stress-test APIs. Fuzz testing reveals vulnerabilities such as buffer overflows, unhandled exceptions, and logical flaws in input handling.
• Enforce strong outbound traffic controls: Many security strategies focus on inbound requests, but compromised APIs can leak sensitive data via outbound traffic. Monitor and restrict outgoing API responses to prevent exfiltration of confidential data or internal infrastructure details.
• Enable API contract testing during development: Use contract testing to ensure that APIs adhere strictly to predefined request and response structures. Contract enforcement catches issues such as schema deviations, which can lead to data exposure or input misinterpretation.
• Implement object-level authorization checks for every resource: Beyond endpoint-level authorization, apply object-level access checks to prevent Broken Object Level Authorization (BOLA) vulnerabilities. Ensure that users can only access resources they are explicitly permitted to interact with.

Real-World Examples of API Security Breaches

Recently, multiple high-profile API security breaches exposed sensitive data and disrupted critical systems. These incidents highlight common vulnerabilities such as broken authentication, misconfigured endpoints, and inadequate input validation:

• US Treasury API key compromise (December 2024): A compromised API key in BeyondTrust’s remote management software enabled a state-sponsored attacker to remotely access workstations and unclassified documents within the US Treasury Department. The breach was mitigated by revoking the key and taking the affected service offline.
• SOLARMAN API vulnerabilities (August 2024): Two critical issues were identified: one endpoint lacked JWT signature verification—allowing attackers to forge tokens and take over accounts—while another returned unfiltered organization data, resulting in excessive sensitive information exposure.
• Cox Communications API breach (June 2024): Unauthenticated endpoints in Cox’s remote management API allowed attackers to impersonate tech support, gaining the ability to query and modify customer device and account data without proper authorization.
• RabbitR1 vulnerability (June 2024): Hardcoded API keys embedded in the Rabbit R1 AI assistant code were exposed, risking unauthorized access to historical AI responses and illustrating the dangers of embedding sensitive keys directly in code.
• Dropbox API keys breach (May 2024): Attackers leveraged flaws in Dropbox Sign’s production API to retrieve API keys, multi‐factor authentication data, and customer records, revealing deficiencies in endpoint protection and monitoring.
• Microsoft Graph API abuse (May 2024): Vulnerabilities in Microsoft Graph API endpoints were exploited to bypass authentication controls, enabling covert data extraction and setting up channels for unauthorized malware communication.
• Dell API breach (May 2024): An exposed API within Dell’s partner portal permitted attackers to access 49 million customer records, reflecting shortcomings in request throttling and anomaly detection in API traffic.
• PandaBuy data breach (April 2024): Exploited API vulnerabilities in the PandaBuy system resulted in unauthorized access to user data for 1.3 million accounts, pointing to inadequate API security testing and misconfigured endpoints.
• Public GitHub repository secrets spill (March 2024): An exposed API configuration in public GitHub repositories allowed extraction of nearly 13 million secrets (API keys, tokens, etc.), underscoring failures in repository access controls and automated secret scanning.
• Spoutible data leak (February 2024): Weak API security on Spoutible’s platform led to exposure of personal data, including bcrypt‐hashed passwords, highlighting gaps in authentication and rate limiting.
• Sensitive messages breach (January 2024): An API flaw enabled attackers to access 650,000 sensitive messages—including Office 365 passwords and confidential communications—demonstrating insufficient input validation and authentication controls.
• Trello API exposure (January 2024): A misconfigured Trello REST API accepted email addresses as query parameters. This allowed attackers to correlate public profile data with email addresses—linking full names to private emails for roughly 15 million users—due to broken object‐level authorization.

6 Best Practices for Preventing API Breaches

Here are some important measures to ensure API security.

1. Implement Strong Authentication and Authorization

APIs must enforce strict authentication and authorization mechanisms to prevent unauthorized access. Implement multi-factor authentication (MFA) to ensure that only verified users can interact with APIs. OAuth 2.0 and OpenID Connect provide secure token-based authentication, reducing the risk of credential theft.

Authorization should follow the principle of least privilege, ensuring users and services have access only to necessary resources. Implement role-based access control (RBAC) and attribute-based access control (ABAC) to restrict API actions based on user roles and attributes. Regularly review access permissions to minimize security risks.

2. Validate All User Input

Proper input validation helps prevent injection attacks, such as SQL injection and cross-site scripting (XSS). APIs should validate and sanitize all incoming data, ensuring it conforms to expected formats and data types. Implement allowlists to accept only predefined values and reject potentially harmful input.

Use parameterized queries to prevent attackers from injecting malicious SQL commands. For JSON and XML payloads, enforce schema validation to prevent unexpected or malformed data from reaching the backend. This approach reduces the risk of data corruption and security vulnerabilities.

3. Employ Rate Limiting and Throttling

Rate limiting and throttling prevent abuse and mitigate denial-of-service (DoS) attacks. Set request limits per user, IP, or API key to control traffic and prevent excessive requests from overwhelming the system. Implement exponential backoff strategies to slow down repeated failed requests.

Use API gateways to enforce rate limits dynamically based on user behavior. Monitoring traffic patterns helps identify abnormal spikes, enabling automated response mechanisms to block malicious traffic before it impacts service availability.

4. Regularly Monitor and Log API Activity

Comprehensive logging and monitoring enable early detection of security incidents. Capture logs for all API requests, authentication attempts, and access control decisions. Ensure logs include timestamps, IP addresses, and request details to enable forensic analysis.

Use real-time monitoring tools to detect anomalies, such as unusual request patterns or unauthorized access attempts. Security information and event management (SIEM) solutions help aggregate and analyze logs, providing alerts when suspicious activities occur. Regularly reviewing logs ensures timely response to potential threats.

5. Keep APIs Updated and Patched

Unpatched vulnerabilities in APIs expose them to known exploits. Regularly update API frameworks, libraries, and dependencies to patch security flaws. Follow secure coding practices to minimize common vulnerabilities such as insecure deserialization and broken authentication.

Conduct routine security audits and penetration testing to identify weaknesses before attackers exploit them. Use automated vulnerability scanning tools to detect misconfigurations and outdated components in the API stack.

6. Use API Gateways and Firewalls

API gateways act as a security layer between clients and backend services, enforcing access control, rate limiting, and authentication policies. They help centralize security management and prevent direct exposure of backend services.

Web application firewalls (WAFs) provide additional protection by filtering malicious traffic and blocking common attack patterns. Configure WAF rules to detect and mitigate threats such as SQL injection, cross-site scripting, and API scraping. Combining API gateways and firewalls strengthens API security and improves overall protection.

Preventing API Security Breaches with Pynt

Pynt is the only AI-powered solution securing from traditional APIs, Modern APIs, and LLM APIs, acting as your personal hacker.

Pynt's leverages an integrated shift-left approach, and unique hack technology using home-grown attack scenarios, to detect real threats, discover APIs, suggest fixes to verified vulnerabilities, thereby eliminating the API attack surface risk.

Thousands of companies rely on Pynt to secure the no. 1 attack surface - APIs, as part of their AppSec strategy. 

Learn more about Pynt