OWASP Top 10 Explained: Critical Web Application Security Risks

The OWASP Top 10 is the definitive list of security risks that every developer should know. Published by the Open Worldwide Application Security Project (OWASP), this list represents a consensus among security professionals about the vulnerabilities most likely to compromise web applications—and the ones attackers actively exploit.

The 2025 edition, the eighth version of this list, analyzed over 175,000 CVE records and 589 Common Weakness Enumerations (CWEs). Two new categories were added, and the list reflects how attack patterns have evolved as applications grow more complex and interconnected. Our analysis of the worst vulnerabilities of 2025 ranked by real-world impact shows how these categories translate to actual breaches.

TL;DR

What it is: A ranked list of the 10 most critical web application security risks
Why it matters: These vulnerabilities are behind the majority of web application breaches
Key takeaway: Addressing these risks during development prevents most common attack vectors

The Complete OWASP Top 10 for 2025

A01: Broken Access Control

Broken access control sits at the top of the list because it appears in roughly 3.7% of all tested applications. This vulnerability occurs when users can access resources or perform actions beyond their intended permissions.

A banking application might let you view your transactions at /account/123. If changing that URL to /account/456 shows someone else's account, that's broken access control. The Facebook data leak in 2021, which exposed 533 million user profiles, stemmed from an API that allowed mass scraping without proper authorization checks.

How to prevent it: Deny access by default, enforce server-side authorization on every request, and log access control failures for monitoring.

A02: Security Misconfiguration

Misconfigurations remain one of the most common—and preventable—vulnerabilities. Default credentials, unnecessary services, overly verbose error messages, and missing security headers all fall into this category.

The Capital One breach demonstrated how a single misconfigured web application firewall, combined with SSRF, exposed data from over 100 million customers. Security teams estimate that 95% of cloud breaches involve human configuration errors. Supply chain attacks like the Notepad++ compromise we covered recently often start with misconfigured build systems.

How to prevent it: Establish repeatable hardening processes, remove unnecessary features, and conduct regular configuration audits.

A03: Software Supply Chain Failures

This is an expansion of the old "Vulnerable and Outdated Components" category, now covering the full spectrum of supply chain risks: malicious packages, compromised maintainers, and tampered build processes.

WannaCry ransomware spread to hundreds of thousands of systems by exploiting unpatched SMBv1 vulnerabilities. More recently, the xz utils backdoor showed how a single compromised dependency could have affected virtually every Linux system. When we track ransomware groups like Qilin, supply chain compromise is increasingly part of their playbook.

How to prevent it: Maintain a software bill of materials (SBOM), monitor dependencies for vulnerabilities, and verify package integrity before deployment.

A04: Cryptographic Failures

Sensitive data needs protection both at rest and in transit. Cryptographic failures occur when encryption is weak, missing, or implemented incorrectly.

Common mistakes include using deprecated algorithms like MD5 or SHA1 for password hashing, hardcoding encryption keys in source code, and transmitting data over HTTP instead of HTTPS. The Uber breach famously involved AWS credentials left in a public GitHub repository—exposing data from 57 million users because those credentials weren't properly protected.

How to prevent it: Classify data and apply appropriate encryption, use strong algorithms and proper key management, and never store secrets in code.

A05: Injection

Injection vulnerabilities—including SQL injection, command injection, and cross-site scripting (XSS)—happen when untrusted data gets sent to an interpreter as part of a command or query.

Despite being well-understood for decades, injection remains dangerous. An attacker might turn a search query into a database dump, or inject JavaScript that steals user sessions. This category encompasses the most CWEs of any item on the list, from low-frequency/high-impact SQL injection to high-frequency XSS attacks. Vulnerabilities like the recent WhatsApp media parsing flaw demonstrate how injection-style issues continue to surface in modern applications.

How to prevent it: Use parameterized queries, validate and sanitize all input, and encode output appropriately for its context.

A06: Insecure Design

Insecure design is different from implementation bugs—it's about fundamental flaws in how an application was architected. No amount of secure coding can fix a design that inherently creates risk.

An example: a password recovery flow that asks security questions is inherently weaker than one using email verification, regardless of how well either is coded. Threat modeling during the design phase catches these issues before any code gets written.

How to prevent it: Integrate threat modeling into the development lifecycle, define and enforce security requirements upfront, and use secure design patterns.

A07: Authentication Failures

Authentication failures let attackers impersonate legitimate users. This includes weak password policies, credential stuffing vulnerabilities, session management flaws, and missing multi-factor authentication.

Uber's business accounts were vulnerable to brute-forcing because the platform didn't rate-limit login attempts. Shopify once had a bug where an attacker could gain collaborator access to any store by exploiting flawed account-linking logic. Our phishing guide covers how attackers often combine credential theft with authentication weaknesses.

How to prevent it: Implement MFA, use strong password policies with breach checking, limit failed login attempts, and use secure session management.

A08: Software or Data Integrity Failures

This category covers code and infrastructure that doesn't verify integrity. CI/CD pipelines without proper checks, auto-updating applications that don't verify signatures, and deserialization of untrusted data all create risk.

The SolarWinds attack inserted malicious code into a trusted update mechanism. Because organizations implicitly trusted software updates, the compromised version deployed across thousands of networks before detection.

How to prevent it: Use digital signatures to verify software and data integrity, review CI/CD pipeline security, and avoid deserializing untrusted data.

A09: Security Logging and Alerting Failures

If you can't see what's happening in your application, you can't respond to attacks. Insufficient logging, missing alerting, and gaps in audit trails let attackers operate undetected.

Many breaches persist for months because organizations lack visibility into their systems. When we report on data breach incidents, delayed detection is a recurring theme—organizations often learn about compromises from external parties rather than their own monitoring.

How to prevent it: Log security-relevant events with sufficient detail, centralize logs, set up real-time alerting for suspicious activity, and test incident response procedures.

A10: Mishandling of Exceptional Conditions

This is new for 2025. It covers improper error handling, logical errors, fail-open conditions, and other issues that arise when applications encounter unexpected situations.

A system that fails open—allowing access when it can't verify authorization—creates obvious security risks. Race conditions, unhandled exceptions that reveal stack traces, and logic errors that bypass security checks all belong here.

How to prevent it: Handle all exceptions properly, fail closed rather than open, test edge cases and error conditions, and avoid exposing sensitive information in error messages.

Using the OWASP Top 10 in Your Organization

The OWASP Top 10 works best as a starting point, not a compliance checklist. Use it to:

Train developers on common vulnerability patterns
Prioritize security testing around high-risk areas
Guide code reviews with specific risks in mind
Inform threat modeling with real-world attack patterns

OWASP provides a Cheat Sheet Series that maps defensive techniques to each Top 10 category. Tools like OWASP ZAP can scan applications for many of these vulnerabilities during development.

The list updates every few years based on new data. The shift from 2021 to 2025 shows how supply chain and configuration issues have become more prominent while the fundamentals—access control, injection, authentication—remain constant threats. Several of these vulnerability classes featured in our top 10 cyber stories of 2025 year-in-review.

For more on secure development practices, explore our security guides. If you're tracking specific vulnerabilities, our vulnerability coverage reports on actively exploited flaws and available patches.

Frequently Asked Questions

How often is the OWASP Top 10 updated?

OWASP releases new versions every few years based on vulnerability data and community input. The 2025 edition followed the 2021 version. Each update reflects shifts in attack patterns and the evolving application landscape.

Is the OWASP Top 10 a compliance requirement?

While not a legal requirement, the OWASP Top 10 is referenced by PCI DSS, HIPAA security guidelines, and other frameworks. Many organizations use it as a baseline for application security programs.

What's the difference between OWASP Top 10 and the API Security Top 10?

OWASP maintains separate Top 10 lists for web applications, APIs, mobile apps, and LLM applications. Each addresses risks specific to that context, though there's overlap in areas like authentication and access control.