XSLT Injection

eXtensible Stylesheet Language Transformation (XSLT) is a powerful language used for transforming XML documents. It allows for the selection of specific nodes and modification of the XML structure, enabling dynamic content generation.

Understanding XSLT

XSLT operates on XML data, which can be structured to include various elements. For example, consider a sample XML document containing information about fruits:

<?xml version="1.0" encoding="UTF-8"?>
<fruits>
    <fruit>
        <name>Apple</name>
        <color>Red</color>
        <size>Medium</size>
    </fruit>
    <fruit>
        <name>Banana</name>
        <color>Yellow</color>
        <size>Medium</size>
    </fruit>
    <fruit>
        <name>Strawberry</name>
        <color>Red</color>
        <size>Small</size>
    </fruit>
</fruits>

XSLT documents are structured similarly to XML but include XSL elements prefixed with xsl:. Common XSL elements include:

• <xsl:template>: Defines a template that matches specific nodes in the XML.

• <xsl:value-of>: Extracts the value of specified XML nodes.

• <xsl:for-each>: Loops over selected XML nodes.

For instance, an XSLT document can be created to output all fruits and their colors:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/fruits">
        Here are all the fruits:
        <xsl:for-each select="fruit">
            <xsl:value-of select="name"/> (<xsl:value-of select="color"/>)
        </xsl:for-each>
    </xsl:template>
</xsl:stylesheet>

This XSLT will produce an output listing all fruits along with their colors.

XSLT Injection

XSLT injection occurs when user input is improperly inserted into XSLT data before it is processed by the XSLT processor. This vulnerability allows attackers to inject additional XSL elements, which the processor will execute during output generation. This can lead to unauthorized data access or manipulation, making it crucial for developers to implement proper input validation and sanitization to prevent such attacks.