The OWASP Top 10, Explained for Founders
A plain-English guide to the OWASP Top 10 web application risks — what each one means, the business impact, and how to fix it, without the jargon.
The OWASP Top 10 is the security industry’s short list of the most critical web application risks, maintained by the Open Worldwide Application Security Project. Auditors, customers, and penetration testers all use it as a baseline. Here it is in plain English — what each category means, why it matters to your business, and the one-line fix.
The OWASP Top 10 at a glance
| Risk | What it means | Fix in one line |
|---|---|---|
| A01 Broken Access Control | Users reach data/actions they shouldn’t (incl. IDOR/BOLA) | Enforce authorization server-side, on every request |
| A02 Cryptographic Failures | Sensitive data exposed in transit or at rest | Use TLS everywhere; encrypt sensitive data |
| A03 Injection | Untrusted input runs as code/queries (SQLi, XSS) | Parameterize queries; encode output |
| A04 Insecure Design | Missing security thinking in the design itself | Threat-model features before building |
| A05 Security Misconfiguration | Insecure defaults, headers, verbose errors | Harden configs; add security headers |
| A06 Vulnerable Components | Outdated libraries with known CVEs | Scan dependencies; patch promptly |
| A07 Auth Failures | Weak login, sessions, or credential handling | MFA, strong sessions, no weak resets |
| A08 Integrity Failures | Untrusted code/updates or insecure deserialization | Verify sources; sign artifacts |
| A09 Logging & Monitoring | Attacks go undetected | Log security events; alert and review |
| A10 SSRF | Server tricked into making attacker-chosen requests | Validate/allow-list outbound URLs |
Where founders should focus first
Broken Access Control (A01) is the one that breaks companies. It is the most common category year after year and includes IDOR/BOLA — one tenant reaching another tenant’s data. Get authorization right before anything else.
The limits of a checklist
The Top 10 tells you what categories to worry about, not whether your app is vulnerable. Automated scanners catch some of A02/A05/A06 but miss A01 and A04 almost entirely, because those require understanding your business logic. That gap is exactly what human-validated penetration testing fills.
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Frequently asked questions
- What is the OWASP Top 10?
- The OWASP Top 10 is a widely referenced, community-driven list of the most critical web application security risks, published by the Open Worldwide Application Security Project. It is used by security teams, auditors, and penetration testers as a baseline for what to test and fix.
- What is the most common OWASP Top 10 risk?
- Broken Access Control (A01) is consistently the most prevalent category. It covers issues like IDOR/BOLA, missing authorization checks, and privilege escalation — flaws where a user can access data or actions they should not.
- Does fixing the OWASP Top 10 make my app secure?
- It is a strong baseline, not a guarantee. The Top 10 covers the most common risk categories, but real assurance comes from human-validated testing against your specific application, including business logic, plus remediation and retesting.
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