XPath is a language used to query and manipulate XML documents. It is widely used in web applications to parse XML documents and extract data for further processing. However, XPath queries can modify data or execute commands on the underlying system. When attackers can inject malicious XPath queries into an application, it can lead to serious security vulnerabilities. This type of attack is known as XPath injection.

XPath injection occurs when an attacker can inject malicious code into an application’s XPath query. This can be done by exploiting vulnerabilities in the application’s input validation or manipulating the application’s input data to bypass input validation. The application can then execute malicious code to access or modify sensitive data or execute arbitrary commands on the underlying system.

An example of XPath injection can be seen in the following XML document:

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Let’s say that an application uses an XPath query to extract the customer’s balance based on their name:

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This query should return the customer’s balance, which in this case is 1000. However, if an attacker can inject malicious code into the query, they could modify the query to return information on all customers or even execute arbitrary commands on the underlying system.
For example, an attacker could inject the following code into the query:

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This code tells the application to move up one level in the XML hierarchy and return all elements at that level. The resulting query would look like this:

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When executed, this query would return all elements at the same level as the customer element, which would be the entire XML document. The attacker could then use this information to extract sensitive data, such as usernames and passwords, or to execute arbitrary commands on the underlying system.
To prevent XPath injection, developers should use input validation to ensure that user input is in the correct format and contains no malicious code. Additionally, developers should use parameterized XPath queries, which treat user input as data rather than code, to prevent attackers from injecting malicious code into the query.

For example, the previous XPath query could be parameterized as follows:

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This query uses a placeholder variable, $name, replaced with user input at runtime. The application treats the user input as data rather than code, preventing attackers from injecting malicious code into the query. If parameterized queries are not possible, developers should use input sanitization to remove any potentially malicious characters from user input. This can help prevent attackers from injecting code into the XPath query.

Conclusion

In summary, XPath injection is a serious security vulnerability attackers can exploit to gain unauthorized access to sensitive data or execute arbitrary commands on the underlying system. To prevent XPath injection, developers should use input validation, parameterized queries, and input sanitization to ensure that user input is safe and does not contain any malicious code. StrongBox IT-Cybersecurity Consulting can help you with secure coding practices and regularly testing for vulnerabilities, developers can help ensure their applications are secure and protect their users’ data