Secure diff

Agents add input paths fast and forget who can reach them. This is a short pass over your own change, done by the author, before anyone else reviews it. It complements a full review; it doesn't replace one.

When it applies

• Any diff that takes outside input, touches auth or permissions, runs commands, builds queries or HTML, reads or writes files by name, fetches URLs, or changes config and defaults.
• Before the first push of agent-written code.

Procedure

1. Secrets

Scan the diff and any new files, including test fixtures, logs and notebooks:

git diff <base> | grep -nEi '(api[_-]?key|secret|token|passw|bearer|private key|-----BEGIN)'

Use a real scanner if installed (gitleaks, trufflehog). Any real value found: remove it, use an env var or the project's secret store, and tell the user the value must be rotated if it was ever committed or pushed.

2. List the new inputs

Every place the diff accepts data it didn't create: request params, headers, bodies, CLI args, env, files, uploads, webhooks, messages, model output. One line each, with file:line.

3. Walk each input to where it is used

4. Authorization

For each new route, action or tool: who may call it, and where is that checked? Check that one user can't read or change another user's object by changing an id. A check in the UI only is not a check.

5. Defaults and failure

New config defaults closed (off, deny, private), not open. Errors fail closed and don't leak stack traces, paths or secrets to the caller. New dependencies are real, maintained packages.

6. Probe what you suspect

For each suspect, run something: a request with ../../etc/passwd, ' OR 1=1 --, <script>, another user's id, an internal URL. Record the command and the result. A probe that gets through is a finding.

Report

Secrets: none found | <removed: where; rotation needed: yes/no>
Inputs: <n>   Findings:
| # | file:line | Issue | Probe | Result | Fixed |
Not covered: <anything you couldn't check>

Rules

• Never paste a found secret into the report; give its location only.
• A suspect is settled by a probe or a quoted guard, not by "looks fine".
• For high-stakes changes (auth, payments, sandboxing), also get an independent review.