Understanding OWASP Top 10 2026
October 28, 2025
A comprehensive breakdown of the latest OWASP Top 10 vulnerabilities and practical guidance on how to protect your applications against each one.
What is OWASP Top 10?
The OWASP Top 10 is a standard awareness document representing the most critical security risks to web applications. Published by the Open Web Application Security Project (OWASP), it is updated periodically based on real-world data collected from security organizations, penetration testing firms, and bug bounty programs worldwide.
The Top 10 serves as a starting point for organizations to prioritize their security efforts and educate developers about common vulnerabilities. It represents consensus among security professionals about which risks deserve the most attention. While not comprehensive, addressing the Top 10 significantly reduces an application's attack surface.
A01: Broken Access Control
Access control failures have risen to become the most critical risk in web applications. These vulnerabilities allow attackers to access resources or perform actions they shouldn't be authorized to do. Common examples include violations of least privilege, bypassing access checks through URL modification, and insecure direct object references (IDOR).
IDOR vulnerabilities are particularly dangerous because they allow attackers to access other users' data by simply changing an identifier in a request. For example, changing "/api/users/123" to "/api/users/124" might expose another user's private information if authorization checks are missing.
Protect against access control failures by implementing server-side access control that cannot be bypassed, denying access by default, logging access control failures and alerting administrators, rate limiting API access, and invalidating session tokens on logout. Automated testing should verify that users cannot access resources belonging to other users or perform unauthorized actions.
A02: Cryptographic Failures
Previously known as Sensitive Data Exposure, this category focuses on failures related to cryptography that lead to sensitive data exposure. These failures can occur when data is transmitted in cleartext, weak cryptographic algorithms are used, encryption keys are poorly managed, or when cryptographic requirements are simply ignored.
Common mistakes include using deprecated algorithms like MD5 or SHA1 for password hashing, storing encryption keys alongside encrypted data, failing to enforce HTTPS, and using weak random number generators for security-sensitive operations.
Best practices include using strong, modern encryption algorithms (AES-256, RSA-2048+), implementing proper key management with regular rotation, ensuring all data is encrypted in transit using TLS 1.3, encrypting sensitive data at rest, and using purpose-built password hashing algorithms like bcrypt or Argon2.
A03: Injection
Injection flaws occur when untrusted data is sent to an interpreter as part of a command or query. SQL injection remains the most common, but injection can occur in NoSQL databases, LDAP queries, OS commands, XML parsers, and even email headers.
A successful injection attack can result in data theft, data modification, denial of service, or complete system compromise. SQL injection has been responsible for some of the largest data breaches in history, exposing millions of user records.
Prevent injection by using parameterized queries or prepared statements that separate code from data, implementing strict input validation using allowlists, escaping special characters when parameterized queries aren't possible, and using ORMs that handle query construction safely. Regular penetration testing should specifically target injection vulnerabilities across all input vectors.
A04: Insecure Design
This category focuses on risks related to fundamental design flaws rather than implementation bugs. No amount of secure coding can fix an insecure design. If an application's architecture has security weaknesses, those weaknesses will persist regardless of how carefully the code is written.
Examples of insecure design include password recovery mechanisms that reveal whether an account exists, applications that don't implement rate limiting on sensitive operations, systems that trust client-side validation, and architectures that don't implement defense in depth.
Address insecure design by incorporating threat modeling early in the development process, using secure design patterns and reference architectures, implementing defense in depth with multiple security layers, and conducting security architecture reviews before implementation begins. The cost of fixing design flaws increases exponentially the later they are discovered.
A05: Security Misconfiguration
Security misconfiguration is one of the most common vulnerabilities and often the easiest to exploit. This category includes missing security hardening, default credentials, overly permissive cloud storage buckets, unnecessary features or services enabled, verbose error messages revealing sensitive information, and missing security headers.
Cloud environments are particularly susceptible to misconfiguration. AWS S3 buckets left publicly accessible, Azure storage accounts with anonymous access, and GCP resources with overly permissive IAM policies have all led to major data breaches.
Implement automated configuration validation using infrastructure as code scanning, use hardened base images and configuration templates, regularly audit cloud configurations against security benchmarks, remove unnecessary features and close unused ports, and ensure error messages don't reveal sensitive system information.
A06: Vulnerable and Outdated Components
Modern applications rely heavily on third-party components, and those components often contain vulnerabilities. When a vulnerability is discovered in a popular library, every application using that library becomes a potential target. The Log4j vulnerability demonstrated how a single flaw in a widely-used component can affect millions of applications worldwide.
Address this risk by maintaining an inventory of all components and their versions, monitoring vulnerability databases for newly discovered flaws, implementing automated dependency scanning in your CI/CD pipeline, and having a process for quickly updating vulnerable components when patches are available.
A07: Identification and Authentication Failures
Authentication vulnerabilities allow attackers to assume other users' identities. Common weaknesses include permitting weak passwords, using weak credential recovery mechanisms, exposing session identifiers in URLs, not rotating session IDs after login, and improper session invalidation.
Implement multi-factor authentication wherever possible, enforce strong password policies, use secure session management practices, implement account lockout after failed login attempts, and ensure session tokens are properly invalidated on logout and timeout.
A08: Software and Data Integrity Failures
These failures occur when code or data is modified without verification. Examples include software updates that aren't verified, insecure CI/CD pipelines that allow unauthorized code injection, and applications that deserialize untrusted data without validation.
Protect against these risks by verifying the integrity of all software updates and patches, securing your CI/CD pipeline with proper access controls and audit logging, using digital signatures for code and data, and avoiding deserialization of untrusted data when possible.
A09: Security Logging and Monitoring Failures
Without proper logging and monitoring, breaches go undetected and attackers can establish persistence. Studies show that most breaches are not discovered for months, giving attackers ample time to extract data or cause damage.
Implement comprehensive logging of security-relevant events, ensure logs are protected from tampering, establish monitoring and alerting for suspicious patterns, and have incident response procedures ready when issues are detected.
A10: Server-Side Request Forgery (SSRF)
SSRF vulnerabilities allow attackers to make the server perform requests to unintended destinations. This can be used to access internal services, cloud metadata endpoints, or other systems that trust the vulnerable server.
Prevent SSRF by validating and sanitizing all user-supplied URLs, using allowlists for permitted destinations, blocking access to internal IP ranges and cloud metadata endpoints, and implementing network segmentation to limit the impact of successful attacks.
Protecting Your Applications
Automated security testing can help identify many of these vulnerabilities before they reach production. Regular penetration testing, security code reviews, and continuous monitoring are essential components of a comprehensive security program. The OWASP Top 10 should be considered a foundation, not a complete security strategy.
Training developers on secure coding practices reduces the introduction of these vulnerabilities in the first place. Combining preventive controls with detective monitoring and responsive incident handling creates a robust security posture that addresses the full lifecycle of security threats.