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 web-cache-deceptiongit 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/web-cache-deception)<a href="https://agentmods.dev/skills/yaklang/hack-skills/web-cache-deception"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/web-cache-deception.svg" alt="Measured on agentmods" height="20"></a>- Socket pass
- Snyk fail
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 | $0.00040 | $0.01641 |
| Opus 5 | $0.00020 | $0.00821 |
| Sonnet 5 | $0.00008 | $0.00328 |
| Haiku 4.5 | $0.00004 | $0.00164 |
Grade A, and why
web-cache-deception 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 3d 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 "Cookie: session=VICTIM" https://target.com/account/profile/x.css Copies of this mod
3 near-identical copies found in the catalogue:
- web-cache-deception — 100% identical, 0 lines differ
- web-cache-deception — 94% identical, 4 lines differ
- web-cache-deception — 92% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 223 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Web Cache Deception — Expert Attack Playbook
AI LOAD INSTRUCTION: Web cache deception and poisoning techniques. Covers path confusion attacks, CDN cache behavior exploitation, cache key manipulation, and the distinction between cache deception (steal data) and cache poisoning (serve malicious content). Presented by Omer Gil at Black Hat 2017 and significantly expanded since.
Advanced Reference
Also load CACHE_POISONING_TECHNIQUES.md when you need:
- Web Cache Poisoning vs Web Cache Deception — clear distinction and attack flow comparison
- Unkeyed header poisoning (X-Forwarded-Host, X-Forwarded-Scheme, X-Original-URL, multiple Host headers)
- Unkeyed parameter poisoning (utm_content, fbclid, callback, reflected but not in cache key)
- Fat GET cache poisoning (body parameters reflected but not keyed)
- Parameter cloaking via semicolons and duplicate parameter parsing differentials
- CDN-specific behavior: Cloudflare, CloudFront, Akamai, Varnish, Fastly (cache key composition, debug headers, ESI)
- Vary header manipulation, cache partitioning attacks, and missing Vary vulnerabilities
1. CORE CONCEPTS
Web Cache Deception (steal authenticated data)
The attacker tricks a victim into requesting their authenticated page at a URL that the cache considers static:
Victim visits: https://target.com/account/profile/nonexistent.css
→ Application ignores "nonexistent.css", serves /account/profile (with auth data)
→ CDN sees .css extension → caches the response
→ Attacker fetches: https://target.com/account/profile/nonexistent.css
→ CDN serves cached authenticated content → attacker reads victim's data
Web Cache Poisoning (serve malicious content)
The attacker manipulates unkeyed request components (headers, cookies) to make the cache store a malicious response:
GET /page HTTP/1.1
Host: target.com
X-Forwarded-Host: evil.com
→ Application generates: <script src="https://evil.com/js/app.js">
→ Cache stores this response
→ Normal users hit cache → load attacker's JavaScript
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.
- 3d ago First seen · 223 lines · 40 tokens per session scan A 5fce05f5c8b8
web-cache-deception is a skill published in the GitHub repository yaklang/hack-skills (2,120 stars, last pushed 2mo ago), licensed MIT. It adds 40 tokens to every session and 1,641 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 2026-09-03.
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