Code Review
Find Vulnerabilities Before They Ship
Review real pull requests for security flaws. Learn to read code the way an attacker does — and catch the bugs that automated scanners miss.
Guided by The Auditor
What it is
Code Review, defined
Secure code review is the last human gate before code reaches production. It's the discipline of reading a change — a pull request — and catching the security bugs, logic errors, and design flaws that would otherwise ship. Not running a scanner: making the judgment call a senior engineer makes on every review — what's really wrong, what's noise, and whether this change is safe to merge.
The career
A skill you get hired for
Every vulnerability in production started as a line of code someone approved. Code review is where that decision gets made — and where most flaws are either caught or missed.
Builds toward
Application Security Engineer
Typical salary
$135K/yr avg
Market demand
500K+ open US roles
Who you'd work alongside
- Application & product security engineers
- Senior and staff engineers gating pull requests
- Security champions embedded on development teams
- Anyone building a secure SDLC or running pre-merge review
The DefendTheOrg approach
How you'll learn it
On Defend the Org you review real GitHub-style pull requests under The Auditor — a mentor who's found zero-days in code that passed three other reviews. You're graded the way a senior reviewer is judged, not on how many bugs you can spot:
Findings — recall and precision
Catching the real issues is half the skill. Spraying comments on clean code costs you points, exactly like it erodes trust on a real team.
Classification
Tag each finding with the right category — SQL injection is Security → Injection, not a logic nit. The taxonomy is the vocabulary of the craft.
Severity & disposition
Does the severity and the block / non-block call match the senior judgment for this finding in this context? A Critical can be non-blocking; a Medium can block.
The final call
Approve, Request Changes, or Comment — and it has to follow from your findings. Most juniors fail this even when their individual findings are right.
Stuck? Get walked through it.
Every Easy and Medium lab has a walkthrough from The Auditor — one hint at a time, with a chance to try each step yourself before the answer. You get three a week, and using one never touches your score. It teaches the reasoning, not the solution.
Try it yourself
A taste of the real lab
This is a simplified, no-signup slice of a Code Review lab — make your call and see how it's graded. The real labs go deeper.
Review this pull request
src/api/users.js — flag the security flaw, classify it, and make the call.
Final call
Push yourself
Where Hard and Expert labs take you
Every skill scales from your first lab to genuinely hard reasoning. Difficulty isn't a bigger wall — it's deeper thinking.
Hard
Hard labs demand non-local reasoning. At least a couple of findings can't be judged from a single line — you trace data flow across files, read the surrounding repository the change now touches, or diff base against head to catch a regression it reintroduced.
Expert
Expert labs are adversarial: compositional vulnerabilities that are safe alone but exploitable combined, fixes that look right but are insufficient for a subtle reason, TOCTOU races, and calibration traps — where the hardest skill is knowing when NOT to request changes.
Start code review training
Hands-on labs built from real engagement data. Learn by doing — guided by The Auditor.