OWASP Top 10 for SaaS: A Practical Audit Checklist (2026)
A practical guide to testing and fixing critical OWASP Top 10 vulnerabilities in your SaaS. Real-world scenarios with Next.js and Supabase code snippets.
The OWASP Top 10 lists the most critical security risks. For a modern SaaS, this translates directly into IDOR (Broken Access Control), exposed secrets, or RLS misconfigurations. This actionable checklist maps OWASP categories to concrete scenarios so you can validate your application security without guessing.
1. Broken Access Control (A01:2021): The Bane of Multi-Tenant SaaS
Broken Access Control is the most critical vulnerability: according to OWASP data, 93% of tested web applications suffer from it. In a SaaS environment, these are typically IDOR (Insecure Direct Object Reference) flaws where a user accesses data from another organization. How to test: Create two test accounts in separate workspaces. Log in with Account A, intercept a request (e.g., GET /api/invoices/123), and replay it using Account B's authentication token. The fix: Never trust the ID provided by the client. Always validate object ownership server-side. With Supabase, this means strict RLS policies. With Next.js, validate the organization inside the Server Action.
// Bad: Trusts the ID only
export async function getInvoice(id: string) {
return db.invoice.findUnique({ where: { id } });
}
// Good: Validates ownership via session tenant
export async function getInvoice(id: string) {
const session = await getSession();
return db.invoice.findFirst({
where: { id, organizationId: session.orgId }
});
}Using UUIDs hides the ID but does not block unauthorized access if the ID is leaked or guessed.
2. Cryptographic Failures (A02:2021): Leaking Sensitive Data
Cryptographic failures occur when sensitive data (passwords, card numbers, API tokens) is transmitted or stored in plaintext. In SaaS setups, this frequently means exposing Stripe or OpenAI keys. How to test: Inspect your production app's network requests. Verify no sensitive data travels over plain HTTP, and analyze your minified JavaScript bundles for prefixes like "sk_live_". The fix: Enforce HSTS (Strict-Transport-Security) for guaranteed HTTPS. In code, ensure private keys are never prefixed with NEXT_PUBLIC_ or VITE_.
3. Injection (A03:2021): Beyond Just SQL
Injection happens when untrusted data is sent to an interpreter as part of a command or query. While modern ORMs like Prisma limit SQL Injection, Cross-Site Scripting (XSS) and Command Injection remain common. How to test: Enter HTML tags or basic XSS payloads (<script>alert(1)</script>) into all input forms and see if they render as executable code. The fix: Always use parameterized queries (built-in for most ORMs). For XSS, let React/Next.js auto-escape content and strictly avoid "dangerouslySetInnerHTML" unless paired with a sanitizer like DOMPurify.
4. Security Misconfiguration (A05:2021): The Silent Error
OWASP estimates that 88% of web applications have misconfigurations. For modern SaaS, this means accidentally public S3 buckets, overly permissive CORS headers, or leaving "Debug" mode active in production. How to test: Scan your API response headers. Check for "Access-Control-Allow-Origin: *". Attempt unauthenticated access to storage bucket files. The fix: Adopt the principle of least privilege by default. Disable detailed error messages in production. You can ensure configurations are solid with the Validra Security Review, which manually audits these setups for €790 in 5 business days.
5. Vulnerable Components (A06:2021): Supply Chain Risks
Using outdated or vulnerable dependencies is responsible for major breaches. Over 70% of apps contain components with known flaws according to OWASP. How to test: Regularly run "npm audit" or "yarn audit". Ensure you aren't using abandoned packages. The fix: Automate Software Composition Analysis (SCA) with tools like Dependabot or Snyk in your CI/CD pipeline. Update regularly, but review major changes to prevent dependency poisoning attacks.
Frequently asked questions
Is the OWASP Top 10 enough to secure my SaaS?
It provides an excellent baseline for critical threats, but must be adapted to your business context (e.g., verifying RLS policies on Supabase). It is the standard used by serious auditors.
How do I test for Broken Access Control?
The best test is manipulating object IDs in URLs or API calls (IDOR) using a secondary, low-privileged test account.
Can automated tools detect the OWASP Top 10?
They easily detect vulnerable components and some injections, but miss nearly 90% of logical access control flaws, which require manual auditing.
How does Validra map to OWASP?
The Validra Security Review is directly based on the OWASP testing methodology, specifically tailored for modern stacks (React, Next.js, Supabase) for optimal coverage.
Is your SaaS ready for production?
Identify critical vulnerabilities before your users do with the Validra Security Review in 5 business days.