What Is the OWASP Top 10? A Complete Guide for 2026

The OWASP Top 10 is the most widely recognized list of critical web application security risks. Published by the Open Web Application Security Project, it helps developers and organizations understand the most dangerous vulnerabilities affecting web applications today.

The OWASP Top 10 (2021 Edition)

A01:2021 — Broken Access Control

Access control ensures users can only access what they are authorized to. When broken, attackers can view other users' data, modify records, or perform admin functions. This moved to #1 from #5 in the previous edition.

A02:2021 — Cryptographic Failures

Previously known as "Sensitive Data Exposure." This covers failures in cryptography that lead to exposure of sensitive data — weak encryption, missing HTTPS, improper certificate validation, and plaintext storage of passwords.

A03:2021 — Injection

Injection attacks occur when untrusted data is sent to an interpreter. SQL injection, Cross-Site Scripting (XSS), and command injection are the most common. A strong Content-Security-Policy header helps mitigate XSS attacks.

A04:2021 — Insecure Design

A new category focusing on design flaws rather than implementation bugs. This includes missing rate limiting, lack of abuse prevention, and absence of threat modeling during development.

A05:2021 — Security Misconfiguration

The most commonly seen issue. Default credentials, unnecessary features enabled, overly permissive error handling, and missing security headers all fall under this category.

A06:2021 — Vulnerable and Outdated Components

Using libraries, frameworks, or dependencies with known vulnerabilities. This includes outdated jQuery versions, unpatched WordPress installations, and EOL PHP versions.

A07:2021 — Identification and Authentication Failures

Weak password policies, missing multi-factor authentication, exposed session tokens, and user enumeration vulnerabilities. Proper session management and cookie security flags are essential.

A08:2021 — Software and Data Integrity Failures

A new category covering issues like missing Subresource Integrity (SRI) hashes on external scripts, insecure deserialization, and CI/CD pipeline vulnerabilities.

A09:2021 — Security Logging and Monitoring Failures

Without proper logging and monitoring, breaches go undetected. Having a security.txt file (RFC 9116) helps security researchers report vulnerabilities to you responsibly.

A10:2021 — Server-Side Request Forgery (SSRF)

SSRF occurs when a web application fetches a remote resource without validating the user-supplied URL. Attackers can use this to access internal services, cloud metadata endpoints, or internal networks.

How to test your website against OWASP Top 10

Our OWASP Top 10 Scanner maps your website's security posture against all ten categories. Available in our Pro Scan (€9.99) and Deep Scan (€29.99), it provides a detailed report with risk levels and fix recommendations for each category.

Why OWASP Top 10 matters for your business

Many compliance frameworks (PCI DSS, SOC 2, ISO 27001) reference the OWASP Top 10. Understanding and addressing these risks is not just good security practice — it is often a business requirement.