HackSkills is an organized knowledge base of installable skills that gives AI agents practical security knowledge across areas such as web security, privilege escalation, reverse engineering, and digital forensics. It is intended for bug bounty work, penetration testing, CTF competitions, and authorized security research. The catalogue entries are the project's own master, category, and topic skills.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add yaklang/hack-skills --skill cors-cross-origin-misconfigurationgit clone --depth 1 https://github.com/yaklang/hack-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/yaklang/hack-skills/cors-cross-origin-misconfiguration)<a href="https://agentmods.dev/skills/yaklang/hack-skills/cors-cross-origin-misconfiguration"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/cors-cross-origin-misconfiguration/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/yaklang/hack-skills/cors-cross-origin-misconfiguration"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/cors-cross-origin-misconfiguration.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk fail
- NVIDIA SkillSpector warn
SkillSpector: 2 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Data Exfiltration · line 104 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
- medium Server-Side Request Forgery · line 230 Code issues a request to a loopback, link-local, or private-range host. This can reach internal services not meant to be exposed and is a common SSRF pivot.Fix: Avoid requests to loopback/link-local/private hosts from skill code. If internal access is intended, document it and validate the target against an allowlist.
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00043 | $0.02369 |
| Opus 5 | $0.00022 | $0.01184 |
| Sonnet 5 | $0.00009 | $0.00474 |
| Haiku 4.5 | $0.00004 | $0.00237 |
Grade A, and why
cors-cross-origin-misconfiguration scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -H "Origin: https://evil.com" https://target.com/api/data -I Copies of this mod
4 near-identical copies found in the catalogue:
- cors-cross-origin-misconfiguration — 100% identical, 0 lines differ
- cors-cross-origin-misconfiguration — 100% identical, 0 lines differ
- cors-cross-origin-misconfiguration — 100% identical, 0 lines differ
- cors-cross-origin-misconfiguration — 98% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 270 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: CORS Misconfiguration — Credentialed Origins, Reflection, and Trust Boundary Errors
AI LOAD INSTRUCTION: Use this skill when browsers can access authenticated APIs cross-origin. Focus on reflected origins, credentialed requests, wildcard trust, parser mistakes, and origin allowlist bypasses. For JSONP hijacking deep dives, same-origin policy internals, honeypot de-anonymization, and CORS vs JSONP comparison, load the companion SCENARIOS.md.
Extended Scenarios
Also load SCENARIOS.md when you need:
- JSONP hijacking complete attack scenario — watering hole +
<script>cross-origin data theft - Honeypot de-anonymization via JSONP — use social platform JSONP endpoints to identify anonymous visitors
- Same-origin policy deep dive — protocol/hostname/port definition,
document.domainsubdomain relaxation and its security risks - CORS vs JSONP technical comparison — methods, error handling, credential behavior, migration path
- CORS exploitation payloads — reflected origin with
credentials: include, null origin via sandboxed iframe - Dual-site attack lab pattern — localhost:8981 (target) + localhost:8982 (attacker) testing setup
1. WHEN TO LOAD THIS SKILL
Load when:
- Responses contain
Access-Control-Allow-Origin,Access-Control-Allow-Credentials, or preflight headers - A browser-based attack path might read authenticated API responses
- JSON endpoints appear protected from CSRF but are readable cross-origin
2. HIGH-VALUE MISCONFIGURATION CHECKS
| Theme | What to Check |
|---|---|
| wildcard with credentials | Access-Control-Allow-Origin: * plus credential support or equivalent broken behavior |
| reflected origin | server echoes arbitrary Origin |
| weak allowlist | suffix, prefix, substring, regex, or mixed-case matching errors |
null origin |
acceptance of sandboxed, file, or serialized origins |
| preflight trust | overbroad methods and headers |
| internal API exposure | admin or tenant data readable cross-origin |
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 11d ago First seen · 270 lines · 43 tokens per session scan A 2de7a95491bc
cors-cross-origin-misconfiguration is a skill published in the GitHub repository yaklang/hack-skills (2,156 stars, last pushed 2mo ago), licensed MIT. It adds 43 tokens to every session and 2,369 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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