In the intricate realm of web vulnerabilities, XML External Entity (XXE) Injection stands as a silent predator, capable of infiltrating web applications through manipulated XML data. These vulnerabilities arise when XML input from user-controlled sources isn’t sanitized, granting an avenue for malevolent exploitation of XML functionalities. XXE vulnerabilities are recognized among the Top 10 Web Security Risks by OWASP for their potential to wreak havoc on web applications and backend servers.
Introduction to XML
XML, designed for versatile data transfer and storage, operates through element trees formed by tags. Elements like the root element, child elements, and entity references define an XML document’s structure. Understanding the anatomy of an XML document is crucial in comprehending the vulnerabilities it may harbor.
Consider an XML document representing an email structure:
<?xml version="1.0" encoding="UTF-8"?>
<email>
<date>01-01-2022</date>
<time>10:00 am UTC</time>
<sender>john@inlanefreight.com</sender>
<recipients>
<to>HR@inlanefreight.com</to>
<cc>
<to>billing@inlanefreight.com</to>
<to>payslips@inlanefreight.com</to>
</cc>
</recipients>
<body>
Hello,
Kindly share with me the invoice for the payment made on January 1, 2022.
Regards,
John
</body>
</email>