hunt-xxe

hunt-xxe is a skill for Claude Code, Codex from uphiago/recon-skills. It costs 127 tokens per session (6,258 once invoked), scanned C, original, MIT.

A security-testing guide for XML external entity (XXE) vulnerabilities, where unsafe XML processing can expose files or reach internal services.

In plain words
What is it for?
It is for testing XML APIs, SVG and office-file uploads, SOAP and SAML sign-in endpoints, and document conversion services.
Why use it?
It helps assess XML parsers and document-processing features that may accept attacker-controlled external references.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: positional $N argument.

Good fit It is for testing XML APIs, SVG and office-file uploads, SOAP and SAML sign-in endpoints, and document conversion services.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/uphiago/recon-skills/hunt-xxe
About the project

Recon Skills is a pack of security-testing skills covering reconnaissance, web applications, APIs, authentication, vulnerability validation, cloud infrastructure, and reporting. Security professionals use it for authorized assessments of systems they own or have written permission to test. The catalogue entries are individual skills from the pack.

uphiago/recon-skills · 1,254 stars · on GitHub · hiago.sh

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 uphiago/recon-skills --skill hunt-xxe
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 hunt-xxe

README.md
[![agentmods](https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-xxe/github.svg)](https://agentmods.dev/skills/uphiago/recon-skills/hunt-xxe)
Your own site
<a href="https://agentmods.dev/skills/uphiago/recon-skills/hunt-xxe"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-xxe/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 hunt-xxe

Your own site · 80×15
<a href="https://agentmods.dev/skills/uphiago/recon-skills/hunt-xxe"><img src="https://agentmods.dev/badge/skills/uphiago/recon-skills/hunt-xxe.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 127 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 6,258 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 2 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 28 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 Privilege Escalation · line 16
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 87
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 111
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 138
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 172
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 229
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 242
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 243
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 244
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 256
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 259
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 270
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 334
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 347
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 369
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 387
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 430
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 441
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 445
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 16
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
How audits are shown
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 5.1 $0.00127 $0.06258
Opus 5 $0.00063 $0.03129
Sonnet 5 $0.00025 $0.01252
Haiku 4.5 $0.00013 $0.00626

Measured 8d ago against content hash 0e92f6244af7, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade C, and why

hunt-xxe scanned grade C 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 8d 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.

Reaches for credential fileshighPrivilege escalation

SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.

- **`hunt-file-upload`** — XXE most often hides inside file-upload features that quietly parse XML (DOCX/XLSX/PPTX, SVG, GPX, KML, OOXML, SOAP attachments). Chain primitive: upload DOCX with malicious `[Content_Types].xm

Makes network callslowCapability

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

curl --max-time 30 --connect-timeout 10 -X POST https://target.com/api/endpoint \
redteam/hunt-xxe/SKILL.md · 445 lines

How it starts

The opening of the file, as written. The whole thing — 445 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Crown Jewel Targets

XXE is a critical-severity vulnerability that consistently pays at the top of bug bounty scales ($5,000–$30,000+) due to its direct path to sensitive data exfiltration and SSRF. Highest-value targets:

  • Large enterprise platforms with XML-heavy backend integrations (finance, logistics, ride-sharing APIs)
  • Domains with file-read capability/etc/passwd, /etc/shadow, internal config files, AWS metadata endpoints
  • Subdomains sharing backend infrastructure — one XXE endpoint can pivot to internal services across dozens of domains (as demonstrated by 26+ Uber domains via a single entry point)
  • API gateways accepting XML content types — especially REST APIs that silently accept Content-Type: application/xml
  • File upload features — SVG, DOCX, XLSX, PDF, PPTX parsers on the server side
  • SAML/SSO endpoints — SAML assertions are XML-based and frequently vulnerable
  • Office/document processing services — any feature that converts or processes user-supplied documents

Attack Surface Signals

URL Patterns

/api/v*/xml
/upload
/import
/parse
/convert
/saml/acs
/sso/saml
/feed
/rss
/sitemap
/webdav
/soap/*
/wsdl
/service.asmx
/xmlrpc
/graphql (multipart with XML)

Request/Response Headers

Content-Type: application/xml
Content-Type: text/xml
Content-Type: application/soap+xml
Content-Type: multipart/form-data  ← check file upload fields
Accept: application/xml
X-Content-Type-Options: (absent — good sign of loose parsing)

JavaScript Patterns (source recon)

// Look for in JS bundles
XMLSerializer
DOMParser
parseFromString
new ActiveXObject("Microsoft.XMLDOM")
$.parseXML(
xml2js
libxmljs
lxml

Tech Stack Signals

  • Java stacks: Spring, Struts, JAX-WS — default XML parsers (SAX, DOM) are XXE-vulnerable without explicit hardening
  • PHP: simplexml_load_string(), DOMDocument::loadXML() — vulnerable by default pre-PHP 8
  • Python: lxml, xml.etree (safe by default), xml.sax (unsafe)
  • Ruby: Nokogiri older versions, REXML
  • Node.js: xml2js, libxmljs, fast-xml-parser (older versions)
  • WSDL/SOAP services: Always test — legacy XML parsing virtually guaranteed
  • File parsers: Apache POI (Java), python-docx, LibreOffice integrations

Read the full file on GitHub · 445 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. 8d ago First seen · 445 lines · 127 tokens per session scan C 0e92f6244af7

Subscribe to this mod's changes

hunt-xxe is a skill published in the GitHub repository uphiago/recon-skills (1,254 stars, last pushed 10d ago), licensed MIT. It adds 127 tokens to every session and 6,258 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it C with 2 findings (reaches for credential files, 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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