Individual skill

cors-security

Strict CORS: no wildcard with credentials, exact-match origin allowlists, sane preflight cache, minimal exposed headers. Use when generating CORS middleware or framework config, setting CORS headers in API Gateway, CloudFront, or Nginx, or reviewing a cross-origin browser-facing endpoint.

skills/cors-security/SKILL.md

Read pinned source

Source commit eaba88102d91df65a9aa6397e8507c315c018f5e

What was checked

Matches the observed repository HEAD: Yes
Scanner rules are current: No
Repository scan complete: No
Skill scan complete: Yes
Observed behavior: Not checked yet
Last checked: Nov 6, 2026

These are observations at the recorded commit, not a guarantee of safety. Review the source before running it.

Install this skill

Choose an agent in your Stack or copy a command below. Commands fetch the pinned commit and copy only this skill directory. Existing destinations are refused. Copying a command does not install anything.

Standard SKILL.md format has not been attested at this commit. No installation command is available; inspect the source.

Repository context

Repository stars (not skill ratings): 23
Repository last updated: Aug 14, 2026
License: MIT

Observed agent integration: No specific integration evidence. Standard SKILL.md installation does not imply verified compatibility.

claude-skills Repository topic
llm Repository topic
security Repository topic
skills Repository topic
engineering Derived category

Files and excerpt

File metadata and permitted, redacted excerpts come from the recorded scan. Source links are pinned to that commit.

Browse files

SKILL.mdcore · 6,187 bytes
references/verifying-findings.mddoc · 3,778 bytes
rules/cors_safe_config.jsonasset · 1,863 bytes
tests/corpus.jsonasset · 2,601 bytes

Read excerpt


# CORS Security

## Rules (for AI agents)

### ALWAYS
- For any non-public endpoint, allow origins from an explicit allowlist. `*` is
  correct only when the resource is intentionally public *and* cross-origin access
  never carries credentials.
- When a cross-origin request carries credentials — the browser's credentials mode is
  `include`, meaning cookies, TLS client certificates, or browser-managed HTTP auth —
  respond with `Access-Control-Allow-Credentials: true` and a **single explicit
  origin**. On a credentialed request every CORS header loses its wildcard meaning:
  `*` in `Allow-Origin`, `Allow-Methods`, `Allow-Headers`, or `Expose-Headers` is read
  as the literal string `"*"` and the browser blocks the response. That is why