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 http-host-header-attacksgit 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/http-host-header-attacks)<a href="https://agentmods.dev/skills/yaklang/hack-skills/http-host-header-attacks"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/http-host-header-attacks/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/http-host-header-attacks"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/http-host-header-attacks.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket warn
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 2 findings, up to high
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 →
- high YARA Match · line 65 YARA rule matched a hack tool or exploit indicator (offensive tools, reconnaissance, privilege escalation, or exploit frameworks).Fix: Remove offensive tool references and exploit code. Legitimate agent skills should not contain penetration testing tools, exploit frameworks, or reconnaissance utilities.
- high Server-Side Request Forgery · line 306 Code accesses a cloud instance metadata endpoint (e.g. 169.254.169.254). A single request can return temporary IAM credentials, making this a high-value SSRF target for credential theft.Fix: Remove access to cloud metadata endpoints unless strictly required. If metadata is needed, restrict it (e.g. IMDSv2 with hop limit) and never expose returned credentials.
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 | $0.00054 | $0.02899 |
| Opus 5.5 | $0.00022 | $0.01160 |
| Sonnet 5.5 | $0.00011 | $0.00580 |
| Haiku 4.5 | $0.00005 | $0.00290 |
Grade B, and why
http-host-header-attacks scanned grade B 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 1mo 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.
Cloud metadata endpointmediumServer-side request forgery
One request to 169.254.169.254 can return temporary IAM credentials.
│ └── Host: 169.254.169.254 → cloud metadata? Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Copies of this mod
6 near-identical copies found in the catalogue:
- http-host-header-attacks — 100% identical, 0 lines differ
- http-host-header-attacks — 100% identical, 0 lines differ
- http-host-header-attacks — 100% identical, 0 lines differ
- http-host-header-attacks — 100% identical, 0 lines differ
- http-host-header-attacks — 100% identical, 0 lines differ
- http-host-header-attacks — 97% identical, 7 lines differ
How it starts
The opening of the file, as written. The whole thing — 324 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: HTTP Host Header Attacks — Injection & Routing Abuse
AI LOAD INSTRUCTION: Covers Host header injection for password reset poisoning, cache poisoning, SSRF via routing, and virtual host bypass. Includes bypass techniques for Host validation and framework-specific behaviors. Base models often miss the double-Host trick, absolute-URI override, and connection-state attacks.
0. RELATED ROUTING
- web-cache-deception when Host injection is combined with cache behavior
- ssrf-server-side-request-forgery when Host header routes requests to internal services
- open-redirect when Host injection causes redirect to attacker domain
- waf-bypass-techniques when Host manipulation helps bypass WAF routing
- request-smuggling when smuggling enables Host header manipulation past front-end validation
- subdomain-takeover when Host routing exposes internal vhosts resolvable via subdomain
1. ATTACK SURFACE
The Host header is used by web applications and infrastructure for:
| Usage | Exploitation |
|---|---|
| URL generation (password reset links, email links) | Inject attacker domain → user clicks link to attacker |
| Virtual host routing | Spoof Host → access internal/admin vhost |
| Cache key component | Inject different Host → poison cache for all users |
| Reverse proxy routing | Host determines backend → SSRF to internal services |
| Access control decisions | Host-based ACLs can be bypassed |
| Canonical URL / SEO redirects | Host injection → open redirect |
2. PASSWORD RESET POISONING
The most common and impactful Host header attack.
How It Works
1. Attacker requests password reset for [email protected]
2. Attacker modifies Host header in the reset request:
POST /forgot-password HTTP/1.1
Host: attacker.com ← injected
[email protected]
3. Server generates reset link using Host header value:
"Click here to reset: https://attacker.com/reset?token=SECRET_TOKEN"
4. Victim receives email, clicks link → token sent to attacker
5. Attacker uses token on real target.com to reset password
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.
- 1mo ago First seen · 324 lines · 54 tokens per session scan B 4c0e5b2b2e3a
http-host-header-attacks is a skill published in the GitHub repository yaklang/hack-skills (2,521 stars, last pushed 1mo ago), licensed MIT. It adds 54 tokens to every session and 2,899 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it B with 1 finding (cloud metadata endpoint). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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