XML injection vulnerabilities occur when user input is improperly incorporated into a server-side XML document or SOAP message. Exploiting this vulnerability involves manipulating XML metacharacters to potentially alter the XML structure. The impact varies based on the function utilizing the XML document, ranging from disrupting application logic to unauthorized actions or unauthorized access to sensitive data.

 
=== "Java"
  ```java
  import org.w3c.dom.Document;
  import org.w3c.dom.Element;
  import javax.xml.parsers.DocumentBuilder;
  import javax.xml.parsers.DocumentBuilderFactory;
  import java.io.StringWriter;
  
  public class XMLInjectionExample {
  
      public static void main(String[] args) {
    // Simulated user input (this should come from a user or external source)
    String userInput = "<maliciousTag>Payload</maliciousTag>";
  
    // Vulnerable XML construction without proper input validation
    String xmlData = "<data>" + userInput + "</data>";
  
    // Process the XML data (vulnerable code)
    processXmlData(xmlData);
      }
  
      public static void processXmlData(String xmlData) {
    try {
        // Parse the XML data
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document document = builder.parse(new org.xml.sax.InputSource(new java.io.StringReader(xmlData)));
  
        // Extract information from the XML (vulnerable code)
        Element root = document.getDocumentElement();
        String content = root.getTextContent();
        System.out.println("Processed XML data: " + content);
    } catch (Exception e) {
        System.err.println("Error processing XML data: " + e.getMessage());
    }
      }
  }
  ```

=== "JavaScript"
  ```javascript
  const userInput = '<maliciousTag>Payload</maliciousTag>';
  
  // Vulnerable XML construction without proper input validation
  const xmlData = '<data>' + userInput + '</data>';
  
  // Process the XML data (vulnerable code)
  processXmlData(xmlData);
  
  function processXmlData(xmlData) {
      try {
    // Parse the XML data
    const parser = new DOMParser();
    const xmlDoc = parser.parseFromString(xmlData, 'text/xml');
  
    // Extract information from the XML (vulnerable code)
    const content = xmlDoc.getElementsByTagName('data')[0].textContent;
    console.log('Processed XML data: ' + content);
      } catch (error) {
    console.error('Error processing XML data: ' + error.message);
      }
  }
  ```

=== "PHP"
  ```php
  <?php
  $userInput = '<maliciousTag>Payload</maliciousTag>';
  
  // Vulnerable XML construction without proper input validation
  $xmlData = '<data>' . $userInput . '</data>';
  
  // Process the XML data (vulnerable code)
  processXmlData($xmlData);
  
  function processXmlData($xmlData) {
      try {
    // Create a new DOMDocument
    $doc = new DOMDocument();
  
    // Load the XML data
    $doc->loadXML($xmlData);
  
    // Extract information from the XML (vulnerable code)
    $content = $doc->getElementsByTagName('data')->item(0)->textContent;
    echo 'Processed XML data: ' . $content . PHP_EOL;
      } catch (Exception $e) {
    echo 'Error processing XML data: ' . $e->getMessage() . PHP_EOL;
      }
  }
  ?>
  ```

