The OWASP Top 10, Explained for Founders Who Aren't Security Engineers

The OWASP Top 10 is the closest thing the security industry has to a universally agreed list of what goes wrong most often in web applications. If you run a SaaS product, someone on your team should understand it at a working level, even if nobody on your team is a security engineer. This is that explanation, written for founders and operators, not for people studying for a security certification.

Each item below includes what it actually means, a plain example of how it shows up in a real product, and what a reasonable first step to address it looks like.

Why this list exists and why it matters to you

OWASP (the Open Worldwide Application Security Project) maintains this list based on real-world data from thousands of applications, updated every few years as attack patterns evolve. It is not theoretical. It is a ranked list of the vulnerability categories that actually get exploited most often, in real breaches, against real companies. If your app has customer data, payment information, or any kind of account system, some subset of this list applies to you whether or not anyone has told you so yet.

1. Broken access control

This is consistently the most common and most damaging category, and it means exactly what it sounds like: a user can access data or perform an action they should not be able to. The classic example is a URL like yourapp.com/invoices/1042. If changing that number to 1043 shows you someone else's invoice, that is broken access control. It happens because the code checked "is this person logged in" but never checked "does this specific record actually belong to this specific person."

First step: audit every endpoint that returns or modifies a specific record, and confirm each one checks ownership, not just authentication.

2. Cryptographic failures

This covers sensitive data (passwords, payment details, personal information) being stored or transmitted without proper protection. Storing passwords in plain text is the extreme version, but subtler failures are more common: using an outdated hashing algorithm, transmitting data over unencrypted connections, or storing API keys in a database without encryption.

First step: confirm passwords are hashed with a modern algorithm (bcrypt or argon2, not MD5 or SHA1), and that your entire app runs over HTTPS with no exceptions.

3. Injection

Injection happens when untrusted input gets treated as executable code instead of data. SQL injection is the most famous version: if user input gets concatenated directly into a database query, an attacker can craft input that changes what the query does entirely. Modern frameworks like Laravel and Rails largely prevent this by default when used correctly, but raw queries or dynamically built strings can reintroduce the risk.

First step: confirm your team uses parameterized queries or an ORM consistently, and specifically audit any place in the codebase using raw SQL.

4. Insecure design

This is a broader category than the others: it covers architectural decisions that create risk regardless of how carefully the code is implemented. A password reset flow that emails the new password in plain text is insecure by design, no matter how well the email-sending code is written. This category rewards thinking about abuse cases during planning, not just during code review.

First step: for any sensitive flow (password reset, payment, account deletion), explicitly ask "how could someone abuse this" before building it, not after.

5. Security misconfiguration

This covers default settings left unchanged, unnecessary features left enabled, and overly detailed error messages that leak information about your system's internals. A production app that shows a full stack trace when something breaks is handing an attacker a map of your technology stack.

First step: confirm your production environment has debug mode disabled and detailed error output turned off, showing users a generic error page instead.

6. Vulnerable and outdated components

Every third-party library and framework you use is a piece of code you did not write and are trusting to be secure. When a vulnerability is discovered in a widely used package, it becomes public knowledge, and unpatched applications become an easy target because the exploit is documented for anyone to use.

First step: run a dependency audit (composer audit for PHP, npm audit for JavaScript) and actually act on what it reports, not just glance at it.

7. Identification and authentication failures

This covers weaknesses in how your app verifies who someone is: weak password requirements, no protection against repeated login attempts, session tokens that do not expire, or session handling that does not properly invalidate on logout.

First step: confirm login attempts are rate-limited, sessions expire after a reasonable period, and multi-factor authentication is at least available for accounts with elevated access.

8. Software and data integrity failures

This covers trusting code or data from a source you have not verified, most commonly through compromised third-party packages or unsigned auto-update mechanisms. Supply chain attacks, where a legitimate-looking package is compromised and distributed to everyone who depends on it, fall in this category.

First step: use lockfiles (composer.lock, package-lock.json) consistently so dependency versions are pinned and reproducible, not silently changing between deployments.

9. Security logging and monitoring failures

If a breach happens and you have no logs showing what was accessed, when, and by whom, you cannot answer the questions a breach forces on you: what was taken, who needs to be notified, is the attacker still active. This category is about visibility after the fact, which matters just as much as prevention.

First step: confirm authentication events, permission changes, and access to sensitive data are logged somewhere you can actually query later.

10. Server-side request forgery

This happens when an application can be tricked into making a request to an internal or unintended destination on the attacker's behalf, often used to reach internal infrastructure that should not be reachable from the outside. It is increasingly common in apps that accept a URL from a user and then fetch it server-side, for example a security scanner, a webhook tester, or a link preview generator.

First step: if your app fetches any user-supplied URL server-side, validate that it cannot resolve to internal or private IP ranges before making the request.

What to do with this list

You do not need to become a security engineer to use this list well. You need to ask, honestly, whether each category has been considered in your app, and if the honest answer is "I don't know," that itself is useful information. It means it is time for either an internal review or an outside audit, ideally before a customer's security questionnaire forces the question.

Frequently Asked Questions

Q: Do I need to fix every item on the OWASP Top 10 before launching a product? A: You need to have deliberately considered each category, which is different from having a perfect score on all ten. Broken access control and injection are the two with the highest real-world impact and deserve priority attention early. The rest matter, but triage based on what your specific application actually exposes.

Q: How often does the OWASP Top 10 change? A: It is updated roughly every three to four years based on aggregated real-world vulnerability data. The categories shift in ranking and occasionally in definition, but broken access control and injection-style vulnerabilities have remained consistently high-impact across every recent version.

Q: Can automated tools catch all of these issues? A: No. Automated scanners are effective at categories like vulnerable dependencies and some misconfiguration issues, but broken access control and insecure design require understanding your specific business logic, which is exactly what manual review by an experienced engineer catches and automated tools miss.

Q: Is the OWASP Top 10 relevant to small apps, or only large enterprise systems? A: It applies at any scale. A five-person startup's customer database is just as valuable to an attacker, and often an easier target, as a large enterprise's, precisely because smaller teams tend to have fewer dedicated security resources.