OWASP Top 10 Explained: A Practical Guide for Developers

The OWASP Top 10 is the industry-standard list of the most critical web application security risks. If you build or run a web app, treating these ten as a baseline checklist will stop the overwhelming majority of real-world attacks. Here's each one in plain English — and how to defend it.

1. Broken Access Control

Users doing things they shouldn't — viewing other people's data, hitting admin endpoints, changing an id in the URL to access someone else's account. Defend it by enforcing authorisation on the server for every request, denying by default, and never trusting the client.

2. Cryptographic Failures

Sensitive data exposed because it wasn't encrypted, or was encrypted weakly. Use TLS everywhere, encrypt sensitive data at rest, use strong modern algorithms, and never roll your own crypto.

3. Injection

Untrusted input changing the meaning of a query or command — SQL injection, command injection, XSS. Use parameterised queries, validate and sanitise input, and encode output.

4. Insecure Design

Flaws baked into the architecture, not just the code. Threat-model early, design for least privilege and fail-safe defaults, and build security requirements into the spec.

5. Security Misconfiguration

Default passwords, verbose errors, open cloud buckets, missing security headers. Harden every environment, automate configuration, and remove anything you don't need.

6. Vulnerable & Outdated Components

That outdated library with a known CVE is an open door. Keep a dependency inventory, patch regularly, and scan your supply chain automatically.

7. Identification & Authentication Failures

Weak passwords, no rate-limiting, broken session handling. Enforce MFA, strong password policies, secure session management and protection against credential stuffing.

8. Software & Data Integrity Failures

Trusting code, updates or CI/CD pipelines that could be tampered with. Verify signatures, lock down your build pipeline, and validate the integrity of what you ship.

9. Security Logging & Monitoring Failures

If you can't see an attack, you can't stop it. Log security-relevant events, monitor and alert, and make sure you can actually detect and respond to an incident.

10. Server-Side Request Forgery (SSRF)

Tricking your server into making requests to places it shouldn't — often to reach internal systems or cloud metadata. Validate and restrict outbound requests, and segment your network.

Where to start

You don't have to fix all ten at once. A web application security audit or penetration test maps which of these actually affect your app, ranked by risk — so you fix what matters first.