cache-attack

cache-attack is a skill for Claude Code, Codex from uphiago/recon-skills. It costs 18 tokens per session (3,062 once invoked), scanned A, original, MIT.

A guide for testing whether a CDN or reverse proxy stores and serves web content incorrectly. A CDN is a network that delivers cached copies of website files closer to users.

In plain words
What is it for?
Checking cache headers, testing cache behavior with unique requests, and investigating web cache poisoning or web cache deception.
Why use it?
It helps authorized testers investigate whether crafted requests could cause harmful content to be cached or expose cached private pages.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/uphiago/recon-skills/cache-attack
Any agent
npx skills add uphiago/recon-skills --skill cache-attack
Clone the repo
git clone --depth 1 https://github.com/uphiago/recon-skills

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 cache-attack

README.md
[![agentmods](https://agentmods.dev/badge/skills/uphiago/recon-skills/cache-attack.svg)](https://agentmods.dev/skills/uphiago/recon-skills/cache-attack)
Your own site
<a href="https://agentmods.dev/skills/uphiago/recon-skills/cache-attack"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/cache-attack.svg" alt="Measured on agentmods" height="20"></a>
Per session 18 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,062 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original 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 $0.00018 $0.03062
Opus 5 $0.00009 $0.01531
Sonnet 5 $0.00004 $0.00612
Haiku 4.5 $0.00002 $0.00306

Measured 4d ago against content hash 769b8192c891, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

cache-attack 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 4d 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.

compatibility: Requires curl
recon/cache-attack/SKILL.md · 281 lines

How it starts

The opening of the file, as written. The whole thing — 281 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Cache Attack Skill

Web Cache Poisoning (WCP) and Web Cache Deception (WCD) methodology. WCP poisons cached pages with malicious content served to other users. WCD tricks the cache into storing sensitive pages that the attacker can then read. Both techniques exploit CDN and reverse-proxy caching behavior on CloudFront, Cloudflare, Fastly, Varnish, and Nginx.

When to Use

  • Target uses a CDN (CloudFront, Cloudflare, Fastly) or reverse proxy (Varnish, Nginx cache).
  • Headers show X-Cache, Age, cf-cache-status, or X-Cache-Hits.
  • After surface recon finds no direct vulnerabilities — pivot to infrastructure layer.
  • Target allows file extension manipulation in URL paths (.css, .json, .js).

Prerequisites

  • terminal with curl.
  • Cache buster parameter for safe testing (?cb=RANDOM).
  • Patience: cache poisoning requires precise timing and may need multiple attempts.

How to Run

# Phase 1: Detect cache
curl --max-time 30 --connect-timeout 10 -skI "https://TARGET/" | grep -iE "age|x-cache|cf-cache-status|via|server"

# Phase 2: Test cache storage (two identical requests)
curl --max-time 30 --connect-timeout 10 -skI "https://TARGET/?cb=TEST1" | grep -iE "x-cache|cf-cache-status"
curl --max-time 30 --connect-timeout 10 -skI "https://TARGET/?cb=TEST1" | grep -iE "x-cache|cf-cache-status"
# Second response should show HIT if caching works

# Phase 3: Test unkeyed header reflection
curl --max-time 30 --connect-timeout 10 -skI "https://TARGET/" -H "X-Forwarded-Host: evil.com" | grep -i "location\|evil.com"

Quick Reference

Web Cache Poisoning (WCP) — attacker poisons cache for victims

Reflection Location Impact Severity
<link rel="canonical"> SEO poisoning Medium
<script src="..."> XSS (stored in cache) Critical
<meta property="og:url"> Phishing (link preview) High
Location: header Mass open redirect High
<form action="..."> Credential theft High
<link rel="stylesheet"> CSS injection Medium

Read the full file on GitHub · 281 lines

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. 4d ago First seen · 281 lines · 18 tokens per session scan A 769b8192c891

Subscribe to this mod's changes

cache-attack is a skill published in the GitHub repository uphiago/recon-skills (1,225 stars, last pushed 2d ago), licensed MIT. It adds 18 tokens to every session and 3,062 once invoked, about $0.0001 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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