Individual skill
web-cors
Exploit CORS misconfiguration to read cross-origin responses (data theft). Load when an API reflects Origin into Access-Control-Allow-Origin, allows credentials cross-origin, or trusts null/subdomains. Signals: ACAO reflects your Origin, ACAC: true, `Origin`-dependent responses.
skills/web/web-cors/SKILL.md
Source commit ee0e0c50d2f6d941a14b73dd85a2b470d0ab976e
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- Last checked
- Nov 7, 2026
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Repository context
- Repository stars (not skill ratings)
- 27
- Repository last updated
- Oct 14, 2026
- License
- MIT
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- agent-skills Repository topic
- ai-agents Repository topic
- ai-security Repository topic
- application-security Repository topic
- blue-team Repository topic
- bug-bounty Repository topic
- claude-code Repository topic
- codex Repository topic
- detection-engineering Repository topic
- gemini Repository topic
- data Derived category
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SKILL.mdcore · 2,110 bytes
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# CORS misconfiguration
## When it applies
An endpoint returns sensitive data and sets CORS headers that let an attacker origin read the
response with the victim's credentials.
## Why it works
CORS lets a server opt-in to cross-origin reads. If it reflects the request `Origin` into
`Access-Control-Allow-Origin` *and* sets `Access-Control-Allow-Credentials: true`, any site can
make the victim's browser send an authenticated request and read the response — cross-origin data theft.
## Method
1. **Probe**: send requests with `Origin: https://evil.com` and inspect response headers.
Vulnerable if ACAO echoes your origin (or `null`) AND ACAC is `true`.