What a Security Code Review Actually Checks — In Plain English

A normal code review asks one question: does this work? A security review asks a harder one: how could someone abuse this? Same code, very different reading. You do not need to write software to understand what a reviewer looks for — and knowing the shape of it helps you tell a thorough team from one that just ships. Most of it maps to a well-known industry checklist, the OWASP Top 10, but here it is without the jargon.

Does it trust input it shouldn't?

Anything typed into a form, added to a web address, or sent from another system is untrusted until proven otherwise. When code takes that input and drops it straight into a database query or a page, attackers can smuggle in commands (SQL injection) or scripts that run in other users' browsers (cross-site scripting). A reviewer checks that every piece of input is validated and safely handled, everywhere — not just on the obvious fields.

Can a user reach what isn't theirs?

Signing in proves who you are; it does not decide what you are allowed to see. A common, serious flaw is when changing a number in a web address — an invoice ID, an account number — quietly shows you someone else's data. A reviewer tries exactly that, deliberately, on every screen that shows private information.

Are the keys left in the door?

Passwords, API keys, and access tokens should never sit inside the source code, yet they routinely do. A reviewer greps for secrets and checks they live in a proper secrets manager instead, where they can be rotated without a code change.

Is it built on cracked foundations?

Modern software leans on dozens of third-party libraries, and old versions accumulate publicly known holes. Reviewing your own code is not enough if a dependency you pulled in three years ago has a critical flaw. A reviewer checks what you depend on and whether it is current.

Does it leak when it breaks?

When something goes wrong, an error page that dumps technical detail — file paths, database structure, stack traces — hands an attacker a map. A reviewer checks that failures are logged privately and shown to users as plain, uninformative messages.

None of this is exotic. It is disciplined, slightly pessimistic reading of ordinary code — assuming the worst about how it will be used, and closing the gaps before someone else finds them.