A Founder's Guide to the OWASP Top 10

The OWASP Top 10 is the closest thing web security has to a shared vocabulary. It is a list, maintained by the Open Worldwide Application Security Project, of the most common and impactful risks in web applications. If you build software, it is worth understanding even if you never write the security code yourself.

This guide walks through the categories in plain language. The goal is not to turn you into a pentester. It is to give you enough context to ask good questions and prioritize the right work.

Why this list matters to you

You do not need to memorize it. You need to recognize the shape of these risks when they show up in a pentest report, a code review, or a conversation with your engineers. Most breaches you read about map to one of these categories. Knowing them is how you tell a serious finding from a shrug.

The categories, in plain terms

1. Broken Access Control

This is when a user can reach something they should not. A regular user editing another user's account by changing an ID in the URL is the classic example. It sits at the top of the list because it is common and the impact is direct.

What to do: Enforce permissions on the server for every request. Never rely on hiding a button in the UI.

2. Cryptographic Failures

Sensitive data that is not properly protected, in transit or at rest. Passwords stored in plain text, traffic served over plain HTTP, secrets in a public repo.

What to do: Encrypt data in transit and at rest. Hash passwords with a modern algorithm. Keep secrets out of your codebase.

3. Injection

Untrusted input that gets treated as a command. SQL injection is the famous one, where input meant to be data ends up rewriting your database query.

What to do: Use parameterized queries and validate input. Modern frameworks handle most of this if you use them as intended.

4. Insecure Design

A flaw in the plan, not the code. If the design assumes something an attacker can break, no amount of clean code saves it. Think of a password reset flow that leaks whether an account exists.

What to do: Threat-model important features before you build them. Ask what an attacker would try.

5. Security Misconfiguration

Default passwords, verbose error messages that leak internals, cloud storage left open to the world. The software is fine, the setup is not.

What to do: Harden defaults, turn off what you do not use, and review your cloud and server configuration regularly.

6. Vulnerable and Outdated Components

The library you imported has a known flaw, and you never updated it. Much of a modern app is other people's code, and their bugs become yours.

What to do: Track your dependencies, watch for advisories, and patch on a schedule instead of a scare.

7. Identification and Authentication Failures

Weak login handling: no protection against password guessing, sessions that never expire, tokens that are easy to predict.

What to do: Support multi-factor auth, rate-limit login attempts, and manage sessions carefully.

8. Software and Data Integrity Failures

Trusting code or data that could have been tampered with. Pulling an update from a source you do not verify, or a build pipeline that anyone can slip code into.

What to do: Verify the integrity of what you deploy and lock down your build pipeline.

9. Security Logging and Monitoring Failures

You got attacked and nobody noticed for months. Without good logs and alerts, you cannot detect or investigate an incident.

What to do: Log security-relevant events, alert on the suspicious ones, and confirm the logs are actually reaching somewhere a human looks.

10. Server-Side Request Forgery

The server is tricked into making a request to somewhere it should not, often reaching internal systems an outside attacker cannot touch directly.

What to do: Validate and restrict the destinations your server will fetch, and do not let user input drive raw outbound requests.

What to do with all this

Do not try to solve all ten at once. Use the list as a lens. When you build a feature, ask which of these it touches. When you read a pentest report, notice which categories your findings fall into, because a cluster in one area points at a habit worth fixing at the source.

Security is a practice, not a project. The Top 10 gives you a map. Where you go from here depends on what you are building and who wants in.