Security Mistakes Killing Startups in 2025

We Audit Startup Codebases. Here's What We Find.

In the past year, we've reviewed security for 20+ startups. The patterns are disturbingly consistent.

These aren't sophisticated attacks. They're basic vulnerabilities that exist because security was "something to add later."

The 7 Most Common Vulnerabilities

1. Broken Access Control (Found in 85% of audits)

The most common, most dangerous vulnerability. Examples:

• User A can view User B's data by changing an ID in the URL
• Admin endpoints accessible to regular users
• API returns more data than the frontend displays

Real impact: One startup exposed 50,000 customer records because their API trusted the client to only request their own data.

Fix: Server-side authorization on every request. Never trust the client.

2. Secrets in Code (Found in 70% of audits)

API keys, database passwords, encryption keys—committed to Git.

"But it's a private repository" doesn't help when:

• A contractor's laptop gets stolen
• An employee leaves and keeps access
• You make the repo public for 5 minutes by accident

Real impact: We found production AWS keys in 3 different repositories. Full account access.

Fix: Environment variables. Secret management. No exceptions.

3. SQL Injection (Found in 40% of audits)

Yes, in 2025. Still happening.

Usually not in the main codebase—in admin tools, reporting scripts, or "temporary" features that became permanent.

Real impact: Full database access. All user data, all credentials, all payment information.

Fix: Parameterized queries. Always. ORMs help but aren't magic.

4. Insecure Session Management (Found in 55% of audits)

Sessions that never expire. Tokens stored in localStorage. No session invalidation on password change.

Real impact: Account takeover persists even after the user "secures" their account.

Fix: Proper session handling. Short expiry times. Invalidation on security events.

5. Missing Rate Limiting (Found in 75% of audits)

Login endpoints with no protection against brute force. API endpoints that can be hammered indefinitely.

Real impact: Credential stuffing attacks succeed. API costs explode from abuse.

Fix: Rate limiting on all public endpoints. Exponential backoff on auth failures.

6. Verbose Error Messages (Found in 60% of audits)

Stack traces in API responses. Database errors exposed to users. Internal paths revealed in error pages.

Real impact: Attackers learn your technology stack, file structure, and potential vulnerabilities.

Fix: Generic error messages for users. Detailed logging for you.

7. Outdated Dependencies (Found in 90% of audits)

npm packages with known CVEs. Frameworks two major versions behind. "If it works, don't update it."

Real impact: Known vulnerabilities with public exploits. Script kiddies can attack you.

Fix: Automated dependency updates. Regular security patching schedule.

The Uncomfortable Truth

Most startups won't get hacked by sophisticated attackers.

They'll get hacked by automated scanners finding known vulnerabilities. By script kiddies running tools they barely understand. By opportunistic attackers who stumbled onto low-hanging fruit.

This is both good news and bad news.

Good: You don't need nation-state-level security. Bad: Basic security failures are embarrassingly common.

What "Good Enough" Security Looks Like

You don't need to be unhackable. You need to be harder to hack than the next target.

Minimum viable security:

1. Access control that actually works - Test it. Break it yourself before attackers do. 2. No secrets in code - Period. Non-negotiable. 3. Updated dependencies - Automated. Not "when we remember." 4. Rate limiting - On everything public-facing. 5. Security headers - CSP, HSTS, X-Frame-Options. Easy wins. 6. Logging and monitoring - Know when something's wrong.

This isn't paranoid. This is baseline.

We Can Help

We offer security audits that find these issues before attackers do. And we build systems with security as a foundation, not an afterthought.

If you're not sure where you stand, start with an assessment.