testing-for-host-header-injection

testing-for-host-header-injection is a skill for Claude Code, Codex from Njones17/AI-agent-master-cyber-skills-list. It costs 36 tokens per session (2,098 once invoked), scanned B, original, no licence file.

A web-security testing guide for finding unsafe handling of the HTTP Host header, which tells a server which site is being requested.

In plain words
What is it for?
Use it to assess Host header handling in web applications and verify related attack paths during authorised security tests.
Why use it?
It helps uncover attacks such as poisoned password-reset links, poisoned web caches, server-side request forgery (SSRF), and incorrect virtual-host routing.

Skill for Claude CodeCodex

Which agent this was written for is unclear — body not stored (licence); the path alone says nothing.

Good fit Use it to assess Host header handling in web applications and verify related attack paths during authorised security tests.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/njones17/ai-agent-master-cyber-skills-list/testing-for-host-header-injection
Install

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.

Any agent
npx skills add Njones17/AI-agent-master-cyber-skills-list --skill testing-for-host-header-injection
Clone the repo
git clone --depth 1 https://github.com/Njones17/AI-agent-master-cyber-skills-list

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for testing-for-host-header-injection

README.md
[![agentmods](https://agentmods.dev/badge/skills/njones17/ai-agent-master-cyber-skills-list/testing-for-host-header-injection/github.svg)](https://agentmods.dev/skills/njones17/ai-agent-master-cyber-skills-list/testing-for-host-header-injection)
Your own site
<a href="https://agentmods.dev/skills/njones17/ai-agent-master-cyber-skills-list/testing-for-host-header-injection"><img src="https://agentmods.dev/badge/skills/njones17/ai-agent-master-cyber-skills-list/testing-for-host-header-injection/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.

agentmods 80×15 button for testing-for-host-header-injection

Your own site · 80×15
<a href="https://agentmods.dev/skills/njones17/ai-agent-master-cyber-skills-list/testing-for-host-header-injection"><img src="https://agentmods.dev/badge/skills/njones17/ai-agent-master-cyber-skills-list/testing-for-host-header-injection.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 36 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,098 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00036 $0.02098
Opus 5 $0.00018 $0.01049
Sonnet 5 $0.00007 $0.00420
Haiku 4.5 $0.00004 $0.00210

Measured 9d ago against content hash 3cd76b1964bb, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade B, and why

testing-for-host-header-injection scanned grade B with 2 findings 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 9d 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.

curl -H "Host: 169.254.169.254" http://target.com/

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -H "Host: evil.com" http://target.com/ -v
skills/application-security/testing-for-host-header-injection/SKILL.md · 214 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

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.

  1. 9d ago First seen · 214 lines · 36 tokens per session scan B 3cd76b1964bb

Subscribe to this mod's changes

testing-for-host-header-injection is a skill published in the GitHub repository Njones17/AI-agent-master-cyber-skills-list (21 stars, last pushed 6mo ago), with no licence file. It adds 36 tokens to every session and 2,098 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it B with 2 findings (cloud metadata endpoint, 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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