XPath Injection: A Tactical Guide

XPATH Injection Attack Image

How Attackers Use XPath Injection to Breach XML-Based Applications

Introduction

In the world of application security, most developers and security teams are familiar with SQL injection. But there's another, less talked about cousin—XPath Injection—which can be just as dangerous, especially in systems that rely on XML data for user authentication and data retrieval. XPath Injection exploits poorly handled user input in XML-based queries, allowing attackers to bypass authentication, extract data, and compromise application logic.

This blog takes a tactical deep dive into XPath Injection: what it is, how it works, and how attackers exploit it to gain unauthorized access to sensitive data.

1. Overview of XPath Injection

XPath Injection, akin to other common injection attacks, specifically targets vulnerabilities within an application’s user input processing system. What sets XPath Injection apart is its exploitation of XPath queries. The fallout? Unauthorized access to data, sidestepping of authentication measures, and in some instances, even remote code execution.

Like SQL Injection manipulates SQL queries, XPath Injection manipulates XPath expressions used to query XML data. This makes it especially dangerous in systems that rely heavily on XML for storage, configuration, or authentication.

2. What is XPath?

XPath (XML Path Language) is a query language used to navigate through elements and attributes in an XML document. It allows developers to search, filter, and select parts of an XML document using path-like expressions.

When used in web applications, XPath is often involved in querying XML databases or files—particularly for operations like login verification, access control, or data retrieval.

Example XML Structure:

<users>
    <user>
        <username>phantom</username>
        <password>blackice</password>
    </user>
    <user>
        <username>reconwolf</username>
        <password>shadowstep</password>
    </user>
</users>

Vulnerable XPath Query:

/users/user[username/text()='<INPUT_USERNAME>' and password/text()='<INPUT_PASSWORD>']

If user input is not sanitized, attackers can manipulate this query to gain unauthorized access.

3. A Step-by-Step Attack Example

Normal Login:

User submits:

• Username: phantom

• Password: blackice

The query becomes:

/users/user[username/text()='phantom' and password/text()='blackice']

Injection Attack:

Attacker submits:

• Username: phantom' or '1'='1

• Password:  

Resulting query:

/users/user[username/text()='phantom' or '1'='1' and password/text()='']

Because '1'='1' always evaluates to true, the condition passes, and authentication is bypassed.

4. Attack Paths and Techniques

A. Authentication Bypass

Classic use-case where attackers log in as any user without valid credentials.

B. Username Enumeration

Varying error messages or timing can expose valid usernames.

C. Data Extraction

Boolean logic, substring analysis, and crafted payloads allow attackers to exfiltrate data from XML documents.

D. Blind XPath Injection

Used when error messages are suppressed. Boolean logic and timing analysis help extract data without direct feedback.

E. Backend File Access

Improper XML parsing and poorly secured file references can expose internal paths or allow directory traversal.

5. Common Payloads for Testing

Use these to probe for injection:

' or '1'='1
' or ''='
'] | //user/*
'] | //user/*[contains(text(),'admin')]

6. Ways to Detect XPath Injection

Manual Testing

• Error Message Analysis – Inputting special characters (like ', ]) may trigger debug responses.

• Behavioral Testing – Observe response differences to crafted inputs.

Automated Testing

• Fuzzing Tools – Tools like FFUF with XPath payload lists.

• Scanners – OWASP ZAP, Burp Suite with plugins.

• Code Review – Static analysis for insecure XPath usage.

7. Mitigating XPath Injection

Input Validation

Sanitize all user input. Use allowlists over blocklists.

Parameterized XPath Queries

If supported by your XML processor, use variables instead of string concatenation.

Least Privilege

Don’t expose sensitive data in the XML if it’s not needed. Keep your access minimal.

Disable Detailed Errors

Never leak the structure of your XPath logic through exception messages.

Patch Regularly

Keep XML libraries and backends updated.

8. Tools for Testing XPath Injection

• Burp Suite with XML plugins

• OWASP ZAP with XML payload fuzzing

• XSStrike (helps test edge cases)

• Custom Scripts for blind injection automation

Community-Built Tool: xghostedpath

One of Ghost Ops Security’s own members, Gh0stsh3ll56, created an open-source tool called xghostedpath, available on GitHub: xghostedpath on GitHub.

This tool automates a wide range of XPath Injection attacks, including:

• Authentication bypass attempts

• Data enumeration

• Blind injection exploitation

• Logging and response analysis

It’s a powerful utility for both red team operators and dev teams looking to validate their XML handling.

9. Conclusion

XPath Injection poses a formidable threat to web applications, particularly when developers overlook the significance of input validation and secure coding. It’s not just a theoretical risk—Ghost Ops has discovered real-world XPath Injection paths that led to full account takeovers, credential leaks, and backend compromise.

By understanding how these attacks work and using tools like xghostedpath to proactively test your systems, you can significantly reduce your exposure.

👉 CTA: Want to see if your system is exposed? Book a brief assessment – we’ll show you how attackers exploit XML and how to lock it down.