Application Security Training

You don't just find the bug —
you patch it.

Vulnfield is a hands-on security lab platform where learners exploit vulnerable applications, capture the flag, patch the vulnerable source, and prove the fix actually holds.

See How It Works → Explore OWASP Labs
server/profile.js
LAB A01 · ACCESS CONTROL
12function getProfile(req, res) {
13− if (user.id !== params.id) {
14− // TODO: add authorization check
15− }
13+ if (user.id !== params.id || !user.isAdmin) {
14+ throw new AuthorizationError()
15+ }
16 return res.json(user.profile)
FIND
EXPLOIT
PATCH
VERIFYING…

Traditional CTF: find the vulnerability and capture the flag. Vulnfield: capture it, patch the vulnerable code, then prove the attack no longer works.

Attack + Remediation
01 / The core loop

One vulnerability,
four commits.

Every lab is the same file, watched through four states. Vulnfield connects offensive security with secure coding by making you own the whole diff — not just the part where you win.

01

Find

Investigate a realistic application and identify the weakness through reconnaissance, testing, and code review.

13if (user.id !== params.id) {
14 // TODO: add check
15}
weakness identified
02

Exploit

Turn the finding into a working attack and capture the flag as proof that the vulnerability is exploitable.

13−if (user.id !== params.id) {
14− // TODO: add check
15−}
flag captured
03

Patch

Open the vulnerable source, understand the root cause, implement a secure fix, and preserve intended functionality.

13−if (user.id !== params.id) {
13+if (id!==params.id||!admin) {
14+ throw new AuthError()
fix implemented
04

Prove

Re-run the attack and platform checks. The lab is complete only when the exploit is blocked without breaking the app.

13+if (id!==params.id||!admin) {
14+ throw new AuthError()
15+}
exploit blocked
02 / Vulnerability curriculum

Built around
OWASP Top 10.

Vulnfield uses the OWASP Top 10 as the foundation for its web application security labs, turning security categories into practical attack-and-remediation exercises.

The current OWASP Top 10 release is 2025. Vulnfield is an independent training platform and is not affiliated with or endorsed by OWASP.
A01:2025
Broken Access Control
Unauthorized actions and data access.
A02:2025
Security Misconfiguration
Unsafe application and environment settings.
A03:2025
Software Supply Chain Failures
Risks across dependencies and delivery.
A04:2025
Cryptographic Failures
Weak protection of sensitive information.
A05:2025
Injection
Untrusted input reaching interpreters.
A06:2025
Insecure Design
Security weaknesses rooted in design.
A07:2025
Authentication Failures
Weak identity and authentication controls.
A08:2025
Software or Data Integrity Failures
Broken trust in software or data.
A09:2025
Security Logging & Alerting Failures
Missing or ineffective security visibility.
A10:2025
Mishandling of Exceptional Conditions
Unsafe behavior during abnormal conditions.
03 / Platform

The lab doesn't end
at the flag.

The remediation phase is a first-class part of the exercise, not an optional explanation after the exploit.

01 / Real Code

Work inside the vulnerable application

Learners don't just answer multiple-choice questions. They inspect and modify application code to understand the root cause.

  • Source-level investigation
  • Root-cause analysis
  • Functional code changes
02 / Functional Fix

Patch without breaking the feature

A secure fix must preserve intended application behavior. The goal is remediation, not simply deleting the vulnerable function.

  • Secure implementation
  • Regression awareness
  • Expected behavior preserved
03 / Verified

Attack again after the patch

The same exploit path becomes the verification mechanism. If the vulnerability remains exploitable, the patch is not complete.

  • Exploit re-test
  • Patch validation
  • Automated checks
04 / Learning

Think like both sides

Students build the mindset of an application security tester while learning how developers actually remove the underlying weakness.

  • Offensive thinking
  • Defensive coding
  • Security verification
04 / Why Vulnfield

From vulnerability
to verified remediation.

− Typical lab

Stop at exploitation.

The learner proves the vulnerability exists and moves to the next challenge.

  • Find the weakness
  • Exploit the weakness
  • Capture the flag
  • Move to the next lab
+ Vulnfield

Close the loop.

The learner owns the full lifecycle from discovery to secure remediation and verification.

  • Find the weakness
  • Exploit and capture the flag
  • Understand the vulnerable code
  • Implement the patch
  • Re-test the original attack
  • Prove the fix works
vuln/field

Find it. Patch it.
Prove it.

A hands-on application security platform built to teach the complete vulnerability lifecycle — exploitation, remediation, and verification.

Build With Vulnfield →