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Starr-delStarr-del/ShipSafe/skills/cors-auditor/SKILL.md

cors-auditor

Skill0 starsChanged 5 months agoMITView on GitHub

Audit CORS configuration in Express, Next.js, FastAPI, or Flask code for security misconfigurations. Use whenever the user mentions CORS errors, 'blocked by CORS policy', cross-origin issues, configures an API for a frontend, or asks why credentials/cookies aren't being sent cross-origin. Also run it before deploying any API. Runs fully offline — no API keys, no network, no credentials.

1 other project uses a version of this.

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The file

We split this skill into the rules it gives an agent

1 rule. About 0 are common, 1 is distinctive, and 0 are very specific to this project.

  • ≈0

    Common · estimate

    Many files like this have a rule of this kind.

  • ≈1

    Distinctive · estimate

    This author's own choices. Worth a look.

  • 0

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Distinctive:

    All paths below are relative to this skill's directory (cors-auditor/).

    line 25

≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

cors-auditor

Part of shipsafe — offline deploy-safety skills. Every script is stdlib-only Python 3.8+; nothing leaves the machine.

python3 scripts/audit_cors.py <project_root> [--json]

Checks, in severity order:

  • WILDCARD_WITH_CREDENTIALS (critical) — browsers reject * + credentials outright, and the tempting 'fix' of reflecting the Origin header turns the API into an account-takeover vector. The correct fix is always an explicit allowlist.
  • REFLECTED_ORIGIN (critical) — req.headers.origin echoed back unvalidated = every website can make authenticated calls as your users.
  • NULL_ORIGIN_ALLOWED (high) — sandboxed iframes can claim Origin: null.
  • WILDCARD_PROD (medium) — legitimate only for truly public read-only APIs; confirm intent with the user.
  • LOCALHOST_IN_LIST (low) — dev config shipped to prod.

Important nuance when interpreting: the user's actual complaint is usually 'CORS is blocking me' and the most common bad advice on the internet is to widen the policy. Diagnose what origin they actually need, and produce the narrowest config that unblocks them — never suggest origin: '*' plus credentials, and never suggest reflecting the request origin without an allowlist check.

Exit codes: 0 clean, 1 findings.

All paths below are relative to this skill's directory (cors-auditor/).

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