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Common API Security Vulnerabilities & Solutions (2025 Guide)

API Security

Shreya Srivastava

May 24, 2025

Common API Security Vulnerabilities and Solutions

APIs are essential for modern software but come with serious security risks. 99% of organizations report API-related security challenges, and 22% experience breaches. These vulnerabilities cost businesses up to $87 billion annually. Here’s a quick breakdown of the most common API vulnerabilities and how to fix them:

Strengthen with OWASP API Top 10 Coverage

The OWASP API Top 10 has become the north star for API security. Many of today’s breaches map directly back to one of these risks. Here’s how they apply in practice:

Broken Object Level Authorization (BOLA): Attackers manipulate IDs to access other users’ data.
Solution: enforce object-level authorization checks, never rely only on IDs in URLs.

Broken Function Level Authorization (BFLA): Normal users escalate privileges by calling admin endpoints.
Solution: enforce RBAC/ABAC, isolate admin routes.
Mass Assignment: Attackers send extra JSON parameters to override hidden fields.
Solution: whitelist parameters, never blindly bind request bodies.
Excessive Data Exposure: APIs return too much information.
Solution: enforce response filtering and schema validation.

Checkout : OWASP API Top 10 explained

Real-World Exploits Developers Miss

Attackers often exploit subtle gaps beyond the obvious. A few examples:

JWT misuse: APIs accept unsigned (alg=none) tokens or fail to rotate keys.
GraphQL abuse: Deeply nested queries cause DoS or reveal hidden fields.
Rate limiting bypass: Attackers spread requests across IPs or use HTTP headers to evade limits.
These issues rarely show up in static scans—they require active security testing.

Solutions You Can Apply Today:

Strong Access Controls: Use Role-Based (RBAC) and Attribute-Based Access Control (ABAC) models.
Secure Authentication: Implement multi-factor authentication (MFA) and secure token protocols like OAuth 2.0.
Limit Data Exposure: Tailor API responses to return only necessary data.
Rate Limiting: Prevent abuse by setting usage limits for API calls.
Secure Configurations: Disable unused methods, restrict access to documentation, and add security headers.

By addressing these vulnerabilities, businesses can protect sensitive data, reduce security risks, and save millions in potential losses. Read on to learn how to secure your APIs effectively and proactively.

Strengthen with OWASP API Top 10 Coverage

The OWASP API Top 10 has become the north star for API security. Many of today’s breaches map directly back to one of these risks. Here’s how they apply in practice:

Broken Object Level Authorization (BOLA): Attackers manipulate IDs to access other users’ data.
Solution: enforce object-level authorization checks, never rely only on IDs in URLs.

Broken Function Level Authorization (BFLA): Normal users escalate privileges by calling admin endpoints.
Solution: enforce RBAC/ABAC, isolate admin routes.
Mass Assignment: Attackers send extra JSON parameters to override hidden fields.
Solution: whitelist parameters, never blindly bind request bodies.
Excessive Data Exposure: APIs return too much information.
Solution: enforce response filtering and schema validation.

Checkout : OWASP API Top 10 explained

Real-World Exploits Developers Miss

Attackers often exploit subtle gaps beyond the obvious. A few examples:

JWT misuse: APIs accept unsigned (alg=none) tokens or fail to rotate keys.
GraphQL abuse: Deeply nested queries cause DoS or reveal hidden fields.
Rate limiting bypass: Attackers spread requests across IPs or use HTTP headers to evade limits.
These issues rarely show up in static scans—they require active security testing.

Solutions You Can Apply Today:

Strong Access Controls: Use Role-Based (RBAC) and Attribute-Based Access Control (ABAC) models.
Secure Authentication: Implement multi-factor authentication (MFA) and secure token protocols like OAuth 2.0.
Limit Data Exposure: Tailor API responses to return only necessary data.
Rate Limiting: Prevent abuse by setting usage limits for API calls.
Secure Configurations: Disable unused methods, restrict access to documentation, and add security headers.

Strengthen with OWASP API Top 10 Coverage

The OWASP API Top 10 has become the north star for API security. Many of today’s breaches map directly back to one of these risks. Here’s how they apply in practice:

Broken Object Level Authorization (BOLA): Attackers manipulate IDs to access other users’ data.
Solution: enforce object-level authorization checks, never rely only on IDs in URLs.

Broken Function Level Authorization (BFLA): Normal users escalate privileges by calling admin endpoints.
Solution: enforce RBAC/ABAC, isolate admin routes.
Mass Assignment: Attackers send extra JSON parameters to override hidden fields.
Solution: whitelist parameters, never blindly bind request bodies.
Excessive Data Exposure: APIs return too much information.
Solution: enforce response filtering and schema validation.

Checkout : OWASP API Top 10 explained

Real-World Exploits Developers Miss

Attackers often exploit subtle gaps beyond the obvious. A few examples:

JWT misuse: APIs accept unsigned (alg=none) tokens or fail to rotate keys.
GraphQL abuse: Deeply nested queries cause DoS or reveal hidden fields.
Rate limiting bypass: Attackers spread requests across IPs or use HTTP headers to evade limits.
These issues rarely show up in static scans—they require active security testing.

Solutions You Can Apply Today:

Strong Access Controls: Use Role-Based (RBAC) and Attribute-Based Access Control (ABAC) models.
Secure Authentication: Implement multi-factor authentication (MFA) and secure token protocols like OAuth 2.0.
Limit Data Exposure: Tailor API responses to return only necessary data.
Rate Limiting: Prevent abuse by setting usage limits for API calls.
Secure Configurations: Disable unused methods, restrict access to documentation, and add security headers.

OWASP API Security Top 10 Course – Secure Your Web Apps

Understanding API vulnerabilities is essential for building strong defenses. The OWASP API Security Top 10 (2023) serves as a guide for recognizing these risks. With 95% of organizations experiencing API security incidents and API traffic now accounting for over 71% of web traffic, the stakes are higher than ever. These vulnerabilities highlight the key areas that require attention to strengthen API security.

The threat landscape is shifting. Attacks targeting API business logic grew by 10% in 2023, now making up 27% of all attacks. Even more alarming, 46% of all account takeover attacks specifically target API endpoints. Below, we break down five critical API vulnerabilities that demand attention.

Vulnerabilities vs Solutions

Vulnerability	Example Attack	Solution
BOLA	Changing `/user/123` to `/user/124`	Object-level checks, RBAC
BFLA	Calling `/admin/delete` as normal user	Role isolation, strict authZ
Mass Assignment	Adding `"role":"admin"` in JSON	Parameter whitelisting
Excessive Data Exposure	Returning PII in response	Response filtering, schema validation
Injection	SQLi via query params	Prepared statements, ORM
Weak Auth	Reusing API keys indefinitely	OAuth2, token rotation

Broken Object Level Authorization (BOLA)

BOLA tops the OWASP list due to its prevalence and severity. This vulnerability arises when APIs fail to check whether users are authorized to access certain data objects. Attackers exploit this by altering object identifiers in API requests, gaining unauthorized access to resources.

The numbers are staggering: BOLA accounts for about 40% of all API attacks, with organizations typically having an average of 1.6 API endpoints vulnerable to this issue. A common attack scenario involves hackers modifying object identifiers in API requests to retrieve or manipulate sensitive data.

Real-world examples from OWASP illustrate the danger. For instance, an e-commerce platform exposed revenue data via endpoints like /shops/{shopName}/revenue_data.json. Attackers manipulated the shop names to access sales data from other stores. In another case, an automobile manufacturer’s remote vehicle control API failed to verify that Vehicle Identification Numbers (VINs) belonged to logged-in users, enabling potential control over vehicles they didn’t own.

The impact goes beyond data breaches. BOLA vulnerabilities can lead to full account takeovers or allow users to delete others’ documents by altering document IDs in requests. Addressing this issue requires implementing strict access controls.

Broken Object Level Authorization (BOLA)

Authentication Failures

Weak or flawed authentication systems are a major security gap for APIs. These failures often involve improper token validation, weak session management, or inadequate user credential verification, allowing attackers to impersonate users or maintain unauthorized access.

A notable example is the Twitter data breach in July 2022. Attackers exploited an API vulnerability to match email addresses and phone numbers with Twitter accounts. This led to the exposure of 5.4 million users’ data, which was later sold on hacking forums. Strengthening authentication methods is critical to mitigating these risks.

Excessive Data Exposure

APIs that return too much data can inadvertently leak sensitive information. Even if client-side applications filter the data before displaying it, attackers can bypass these filters by directly accessing the API.

This issue consistently ranks among the top three OWASP API threats. In 2023, 50% of organizations reported data breaches tied to API vulnerabilities, with excessive data exposure playing a major role. The scale of the problem is immense - over 155.8 million individuals in the U.S. were affected by data breaches in 2020 alone.

Developers often create this vulnerability by returning all available data without considering its sensitivity. Attackers exploit this by directly querying APIs, bypassing any client-side filters. Implementing data minimization strategies is key to addressing this risk.

Unrestricted Resource Consumption

Previously known as "Lack of Resources & Rate Limiting", this vulnerability allows attackers to overwhelm API infrastructure by consuming excessive resources like bandwidth, CPU, memory, or storage. These attacks can also target external services, such as email or SMS systems, leading to financial strain due to per-request charges.

Without proper rate limiting, such attacks can cause denial of service or escalate operational costs. For instance, with enterprises processing an average of 1.5 billion API calls, resource management becomes vital for both performance and cost control. Implementing rate-limiting controls effectively mitigates this threat.

Security Misconfigurations

APIs often come with complex configurations, which, if improperly managed, can introduce vulnerabilities. Common misconfigurations include exposed API documentation, insecure defaults, unnecessary HTTP methods, missing security headers, and verbose error messages. These oversights give attackers critical insights into system architecture and potential entry points.

The 2022 attack on Ukraine’s power grid underscores the risks. The Sandworm hacker group exploited an API vulnerability in a third-party component, gaining access to circuit breakers in an electrical substation and causing widespread power outages. This incident highlights how misconfigurations can lead to consequences far beyond data theft, impacting critical infrastructure and public safety. Adopting secure configuration practices is essential to prevent such exposures.

Vulnerability	Attack Frequency	Primary Risk
Broken Object Level Authorization	40% of API attacks	Unauthorized data access, account takeover
Authentication Failures	46% of account takeovers	Identity compromise, persistent access
Excessive Data Exposure	Top 3 OWASP threats	Sensitive data leakage, privacy violations
Unrestricted Resource Consumption	Growing threat	Service disruption, cost escalation
Security Misconfigurations	Infrastructure-wide impact	System exposure, critical service disruption

These vulnerabilities often overlap, amplifying their combined impact. For example, a misconfigured API with weak authentication and excessive data exposure creates multiple attack vectors that skilled adversaries can exploit. Recognizing these vulnerabilities is the first step toward implementing effective solutions, which will be explored in the next section.

Vulnerabilities vs Solutions

Vulnerability	Example Attack	Solution
BOLA	Changing `/user/123` to `/user/124`	Object-level checks, RBAC
BFLA	Calling `/admin/delete` as normal user	Role isolation, strict authZ
Mass Assignment	Adding `"role":"admin"` in JSON	Parameter whitelisting
Excessive Data Exposure	Returning PII in response	Response filtering, schema validation
Injection	SQLi via query params	Prepared statements, ORM
Weak Auth	Reusing API keys indefinitely	OAuth2, token rotation

Broken Object Level Authorization (BOLA)

Authentication Failures

Excessive Data Exposure

Unrestricted Resource Consumption

Security Misconfigurations

Vulnerability	Attack Frequency	Primary Risk
Broken Object Level Authorization	40% of API attacks	Unauthorized data access, account takeover
Authentication Failures	46% of account takeovers	Identity compromise, persistent access
Excessive Data Exposure	Top 3 OWASP threats	Sensitive data leakage, privacy violations
Unrestricted Resource Consumption	Growing threat	Service disruption, cost escalation
Security Misconfigurations	Infrastructure-wide impact	System exposure, critical service disruption

Vulnerabilities vs Solutions

Vulnerability	Example Attack	Solution
BOLA	Changing `/user/123` to `/user/124`	Object-level checks, RBAC
BFLA	Calling `/admin/delete` as normal user	Role isolation, strict authZ
Mass Assignment	Adding `"role":"admin"` in JSON	Parameter whitelisting
Excessive Data Exposure	Returning PII in response	Response filtering, schema validation
Injection	SQLi via query params	Prepared statements, ORM
Weak Auth	Reusing API keys indefinitely	OAuth2, token rotation

Broken Object Level Authorization (BOLA)

Authentication Failures

Excessive Data Exposure

Unrestricted Resource Consumption

Security Misconfigurations

Vulnerability	Attack Frequency	Primary Risk
Broken Object Level Authorization	40% of API attacks	Unauthorized data access, account takeover
Authentication Failures	46% of account takeovers	Identity compromise, persistent access
Excessive Data Exposure	Top 3 OWASP threats	Sensitive data leakage, privacy violations
Unrestricted Resource Consumption	Growing threat	Service disruption, cost escalation
Security Misconfigurations	Infrastructure-wide impact	System exposure, critical service disruption

Addressing API vulnerabilities requires specific, actionable steps. Below are practical measures you can take to secure your APIs effectively.

Set Up Strong Access Control

To prevent unauthorized access, implement robust access control measures. Two effective models are Role-Based Access Control (RBAC) and Attribute-Based Access Control (ABAC). RBAC assigns permissions based on user roles, while ABAC uses user attributes to make more granular authorization decisions. A hybrid approach works well - use RBAC for broader permissions and ABAC for more detailed controls.

OAuth access tokens are a reliable foundation for these controls, as their claims provide trustworthy attributes for ABAC systems. Avoid using attributes passed in headers, query strings, or request bodies since these can be spoofed. Instead, rely on tamper-proof sources for authorization attributes.

For growing API ecosystems, tools like Open Policy Agent can centralize and streamline policy management across services. Always enforce authorization checks at each API endpoint to ensure users have the necessary permissions for the requested resource.

Once access control is in place, focus on securing authentication methods.

Secure Authentication Methods

Authentication is the cornerstone of API security. A lack of proper authentication can lead to catastrophic breaches, as seen in the 2021 Parler incident, where hacktivists exploited weak authentication to scrape 70TB of data.

Strengthen your APIs with multi-factor authentication (MFA), adding an extra layer beyond passwords or tokens. For token-based systems, use secure protocols like OAuth 2.0 and JWT with short expiration times to limit token misuse. Incorporate token rotation with automatic refresh to further reduce risks.

Always transmit tokens over HTTPS and store them securely to prevent leaks. Protect against brute-force attacks with measures like account lockouts, rate limiting, and CAPTCHA challenges. Regularly monitor authentication logs for suspicious activity that could signal an ongoing attack.

With authentication secured, the next step is to minimize data exposure.

Reduce Data Exposure

Design your APIs to limit data exposure from the outset. Instead of sending all available data and filtering it on the client side, tailor your endpoints to return only the data required for each specific operation.

Use response filtering and field-level permissions to control which data fields are accessible by different user roles. For example, a public user profile endpoint should only return non-sensitive information, while an account management endpoint may provide additional details.

GraphQL can be particularly useful here, as it allows clients to request only the fields they need, reducing the likelihood of accidental data exposure. For REST APIs, create specific endpoints for distinct use cases and define clear response schemas. Regularly audit these schemas to ensure they align with current business needs.

Beyond data handling, managing API traffic is another critical step.

Control Rate Limits and Resources

Rate limiting protects APIs from abuse and overuse by setting limits on how often they can be accessed within a given timeframe. Choose an algorithm suited to your traffic patterns - for steady traffic, Fixed Window algorithms work well, while Sliding Window or Token Bucket methods are better for handling bursts.

Implement tiered rate limiting to differentiate between user roles and API endpoints. Sensitive operations should have stricter limits. Dynamic rate limits that adjust based on real-time conditions, such as server load or detected attacks, add an extra layer of protection.

Monitor rate limits continuously, track usage patterns, and provide users with clear retry guidelines when limits are reached.

Finally, secure your API configurations to prevent vulnerabilities.

Security in CI/CD Pipelines

Security checks must live inside your CI/CD pipeline, not as a one-off scan. Recommended practices:

Run OWASP ZAP in Docker against staging APIs.

Add SAST (static analysis) and SCA (dependency scans) at build time.
Include negative API tests in Postman/Newman collections (e.g., expired tokens, broken scopes).
Fail builds if security thresholds (e.g., no high-severity CVEs, auth tests pass) are not met.

CI Example (GitHub Actions):

- name: OWASP ZAP Baseline Scan
  uses: zaproxy/action-baseline@v0.8.0
  with:
    target: ${{ secrets.STAGING_API_URL }}
    rules_file_name: .zap/rules.tsv
    cmd_options: "-a"

Secure API Configurations

Proper configuration management is essential for API security. Start by disabling unused HTTP methods on your endpoints. For example, if an endpoint only requires GET and POST, explicitly disable methods like PUT, DELETE, and PATCH to reduce the attack surface.

Restrict access to API documentation in production environments. While detailed documentation is helpful for developers, it can expose sensitive information if publicly accessible. Use authentication to control access to this documentation.

Add security headers like Content Security Policy (CSP), X-Frame-Options, and X-Content-Type-Options to protect against common attack vectors. Error messages should be generic, such as "Authentication failed", to avoid revealing detailed system information.

Conduct regular configuration audits to catch misconfigurations before they lead to security incidents. Automated tools can help identify issues like exposed debug endpoints, default credentials, or overly permissive CORS policies. Perform these audits periodically, especially after major infrastructure changes.

Addressing API vulnerabilities requires specific, actionable steps. Below are practical measures you can take to secure your APIs effectively.

Set Up Strong Access Control

Once access control is in place, focus on securing authentication methods.

Secure Authentication Methods

With authentication secured, the next step is to minimize data exposure.

Reduce Data Exposure

Beyond data handling, managing API traffic is another critical step.

Control Rate Limits and Resources

Monitor rate limits continuously, track usage patterns, and provide users with clear retry guidelines when limits are reached.

Finally, secure your API configurations to prevent vulnerabilities.

Security in CI/CD Pipelines

Security checks must live inside your CI/CD pipeline, not as a one-off scan. Recommended practices:

Run OWASP ZAP in Docker against staging APIs.

Add SAST (static analysis) and SCA (dependency scans) at build time.
Include negative API tests in Postman/Newman collections (e.g., expired tokens, broken scopes).
Fail builds if security thresholds (e.g., no high-severity CVEs, auth tests pass) are not met.

CI Example (GitHub Actions):

- name: OWASP ZAP Baseline Scan
  uses: zaproxy/action-baseline@v0.8.0
  with:
    target: ${{ secrets.STAGING_API_URL }}
    rules_file_name: .zap/rules.tsv
    cmd_options: "-a"

Secure API Configurations

Addressing API vulnerabilities requires specific, actionable steps. Below are practical measures you can take to secure your APIs effectively.

Set Up Strong Access Control

Once access control is in place, focus on securing authentication methods.

Secure Authentication Methods

With authentication secured, the next step is to minimize data exposure.

Reduce Data Exposure

Beyond data handling, managing API traffic is another critical step.

Control Rate Limits and Resources

Monitor rate limits continuously, track usage patterns, and provide users with clear retry guidelines when limits are reached.

Finally, secure your API configurations to prevent vulnerabilities.

Security in CI/CD Pipelines

Security checks must live inside your CI/CD pipeline, not as a one-off scan. Recommended practices:

Run OWASP ZAP in Docker against staging APIs.

Add SAST (static analysis) and SCA (dependency scans) at build time.
Include negative API tests in Postman/Newman collections (e.g., expired tokens, broken scopes).
Fail builds if security thresholds (e.g., no high-severity CVEs, auth tests pass) are not met.

CI Example (GitHub Actions):

- name: OWASP ZAP Baseline Scan
  uses: zaproxy/action-baseline@v0.8.0
  with:
    target: ${{ secrets.STAGING_API_URL }}
    rules_file_name: .zap/rules.tsv
    cmd_options: "-a"

Secure API Configurations

API security has become a critical focus for businesses, especially with Gartner predicting that API abuses will soon dominate enterprise attack methods. Companies that implement structured API security measures not only protect sensitive data but also gain a competitive edge by showing their dedication to user privacy and data protection.

Add Advanced Mitigation Strategies

Beyond developer fixes, organizations should enforce system-level protections:

API Gateways: Centralized authN/authZ, quotas, and schema validation.
Rate limiting & throttling: Defend against brute force and DoS.
Runtime Application Self-Protection (RASP): Block malicious payloads at runtime.
Observability & logging: Collect metrics (latency, error spikes, unusual IPs) to detect abuse early.
Zero Trust principles: Validate every call, even inside private networks.

Checkout: API monitoring and logging

Main Vulnerabilities to Watch

From our breakdown of vulnerabilities, these are the key areas to monitor closely: BOLA (Broken Object Level Authorization), authentication failures, excessive data exposure, unrestricted resource consumption, and misconfigurations. Additionally, relying too heavily on APIs without maintaining strong security practices - like proper input validation - can create significant risks.

As the OWASP Foundation explains:

"APIs are a foundational element of innovation in today's app-driven world... By nature, APIs expose application logic and sensitive data such as Personally Identifiable Information (PII) and because of this have increasingly become a target for attackers"

Next Steps for Your Team

To move forward, your team needs to adopt a proactive and ongoing approach to API security. Regularly audit your API environment, apply patches promptly, and have a clear incident response plan in place.

You might also consider advanced tools like Qodex to simplify and automate your API security processes. These tools can help with continuous monitoring and security testing, ensuring your defenses stay ahead of evolving threats.

Add Advanced Mitigation Strategies

Beyond developer fixes, organizations should enforce system-level protections:

API Gateways: Centralized authN/authZ, quotas, and schema validation.
Rate limiting & throttling: Defend against brute force and DoS.
Runtime Application Self-Protection (RASP): Block malicious payloads at runtime.
Observability & logging: Collect metrics (latency, error spikes, unusual IPs) to detect abuse early.
Zero Trust principles: Validate every call, even inside private networks.

Checkout: API monitoring and logging

Main Vulnerabilities to Watch

As the OWASP Foundation explains:

Next Steps for Your Team

Add Advanced Mitigation Strategies

Beyond developer fixes, organizations should enforce system-level protections:

API Gateways: Centralized authN/authZ, quotas, and schema validation.
Rate limiting & throttling: Defend against brute force and DoS.
Runtime Application Self-Protection (RASP): Block malicious payloads at runtime.
Observability & logging: Collect metrics (latency, error spikes, unusual IPs) to detect abuse early.
Zero Trust principles: Validate every call, even inside private networks.

Checkout: API monitoring and logging