xxe

xxe is a skill for Claude Code, Codex from PurpleAILAB/Decepticon. It costs 25 tokens per session (216 once invoked), scanned A, original, Apache-2.0.

A guide to finding XML External Entity flaws, where an unsafe XML parser may read local files or make requests to internal services.

In plain words
What is it for?
It is for locating unsafe XML parsers and safely checking file-read and server-side request forgery impact.
Why use it?
It helps determine whether XML input can access data or systems beyond what the application should reach.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit It is for locating unsafe XML parsers and safely checking file-read and server-side request forgery impact.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/purpleailab/decepticon/xxe
About the project

Decepticon is an autonomous red-team agent that coordinates AI agents, security tools, sandboxes, and supporting services for authorized cybersecurity assessments. Security researchers and red teams can run it through its Docker stack, cloud service, command-line interface, or Python SDK, with the catalogue entries representing its available skills.

PurpleAILAB/Decepticon · 5,491 stars · on GitHub · decepticon.red

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 PurpleAILAB/Decepticon --skill xxe
Clone the repo
git clone --depth 1 https://github.com/PurpleAILAB/Decepticon

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 xxe

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

Your own site · 80×15
<a href="https://agentmods.dev/skills/purpleailab/decepticon/xxe"><img src="https://agentmods.dev/badge/skills/purpleailab/decepticon/xxe.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 216 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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: 1 finding, 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 22
    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 $0.00025 $0.00216
Opus 5 $0.00013 $0.00108
Sonnet 5 $0.00005 $0.00043
Haiku 4.5 $0.00003 $0.00022

Measured 9d ago against content hash fd245dfa12c1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

xxe scanned grade A with 0 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

packages/decepticon/decepticon/skills/standard/analyst/xxe/SKILL.md · 28 lines

What it actually says

XXE Playbook

Find parser sinks

  • Java: DocumentBuilderFactory, SAXParserFactory, XMLInputFactory
  • Python: lxml.etree, xml.dom.minidom, xml.sax
  • .NET: XmlDocument, XDocument, XmlReader

Dangerous defaults

  • DTD enabled
  • External entities enabled
  • Network/file entity resolution enabled

Payloads

  • File read: entity to file:///etc/passwd
  • SSRF: entity to internal URL (metadata service, localhost admin)

Validation

  • Positive: parser output contains file content or internal response markers.
  • Negative: same XML without entity expansion must not leak content.
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 · 28 lines · 25 tokens per session scan A fd245dfa12c1

Subscribe to this mod's changes

xxe is a skill published in the GitHub repository PurpleAILAB/Decepticon (5,491 stars, last pushed 13d ago), licensed Apache-2.0. It adds 25 tokens to every session and 216 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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