To mitigate XML injection vulnerabilities, consider:

- Implement proper input validation and sanitization techniques. 
- Validate user input against expected formats, and sanitize it by removing or escaping characters that could be interpreted as XML tags or entities. 
- Consider using secure XML parsing libraries or APIs that handle data binding securely.

=== "Dart"
	```dart
	import 'dart:convert';
	import 'dart:io';
	
	import 'package:flutter/material.dart';
	import 'package:path_provider/path_provider.dart';
	import 'package:xml/xml.dart';
	
	void main() {
	  runApp(MyApp());
	}
	
	class MyApp extends StatelessWidget {
	  @override
	  Widget build(BuildContext context) {
	    return MaterialApp(
	      title: 'XML Injection Demo',
	      theme: ThemeData(
	        primarySwatch: Colors.blue,
	      ),
	      home: MyHomePage(),
	    );
	  }
	}
	
	class MyHomePage extends StatefulWidget {
	  @override
	  _MyHomePageState createState() => _MyHomePageState();
	}
	
	class _MyHomePageState extends State<MyHomePage> {
	  final TextEditingController _usernameController = TextEditingController();
	  final TextEditingController _passwordController = TextEditingController();
	
	  @override
	  void dispose() {
	    _usernameController.dispose();
	    _passwordController.dispose();
	    super.dispose();
	  }
	
	  Future<void> saveConfigFile() async {
	    final directory = await getApplicationDocumentsDirectory();
	    final configFile = File('${directory.path}/config.xml');
	
	    // Create XML data
	    final builder = XmlBuilder();
	    builder.processing('xml', 'version="1.0"');
	    builder.element('root', nest: () {
	      builder.element('username', nest: _usernameController.text);
	      builder.element('password', nest: _passwordController.text);
	    });
	    final xmlData = builder.build().toXmlString(pretty: true);
	
	    // Save the XML to the configuration file
	    await configFile.writeAsString(xmlData);
	  }
	
	  void login() {
	    final username = _usernameController.text;
	    final password = _passwordController.text;
	
	    // Perform login logic
	    print('Performing login with username: $username and password: $password');
	  }
	
	  @override
	  Widget build(BuildContext context) {
	    return Scaffold(
	      appBar: AppBar(
	        title: Text('XML Injection Demo'),
	      ),
	      body: Padding(
	        padding: EdgeInsets.all(16.0),
	        child: Column(
	          crossAxisAlignment: CrossAxisAlignment.start,
	          children: [
	            Text('Enter username:'),
	            TextField(
	              controller: _usernameController,
	            ),
	            SizedBox(height: 16.0),
	            Text('Enter password:'),
	            TextField(
	              controller: _passwordController,
	              obscureText: true,
	            ),
	            SizedBox(height: 16.0),
	            ElevatedButton(
	              onPressed: () async {
	                await saveConfigFile();
	                login();
	              },
	              child: Text('Login'),
	            ),
	          ],
	        ),
	      ),
	    );
	  }
	}
	```



=== "Swift"
	```swift
	import Foundation
	
	func main() {
	    let configFilePath = "config.xml"
	    
	    // Load configuration file
	    guard let configFileURL = Bundle.main.url(forResource: "config", withExtension: "xml") else {
	        print("Failed to load configuration file")
	        return
	    }
	    
	    guard let xmlData = try? Data(contentsOf: configFileURL) else {
	        print("Failed to read configuration file")
	        return
	    }
	    
	    // Parse XML
	    let xmlDoc: XMLDocument
	    do {
	        xmlDoc = try XMLDocument(data: xmlData, options: .documentTidyXML)
	    } catch {
	        print("Failed to parse XML: \(error)")
	        return
	    }
	    
	    guard let root = xmlDoc.rootElement() else {
	        print("Invalid XML structure")
	        return
	    }
	    
	    // Read configuration values from user input
	    guard let username = getUserInput(prompt: "Enter username:"), let password = getUserInput(prompt: "Enter password:") else {
	        print("Invalid input")
	        return
	    }
	    
	    // Update configuration values in XML
	    if let usernameElement = root.elements(forName: "username").first {
	        usernameElement.stringValue = username
	    }
	    
	    if let passwordElement = root.elements(forName: "password").first {
	        passwordElement.stringValue = password
	    }
	    
	    // Save the modified XML back to the configuration file
	    guard let modifiedXmlData = xmlDoc.xmlData(options: .nodePrettyPrint) else {
	        print("Failed to generate modified XML")
	        return
	    }
	    
	    do {
	        try modifiedXmlData.write(to: configFileURL)
	    } catch {
	        print("Failed to write modified XML to file: \(error)")
	        return
	    }
	    
	    // Use the configuration values
	    login(username: username, password: password)
	}
	
	func getUserInput(prompt: String) -> String? {
	    print(prompt, terminator: " ")
	    return readLine()
	}
	
	func login(username: String, password: String) {
	    // Perform login logic
	    print("Performing login with username: \(username) and password: \(password)")
	}
	
	// Start the program
	main()
	```



=== "Kotlin"
	```kotlin
	import android.os.Bundle
	import android.widget.Button
	import android.widget.EditText
	import android.widget.Toast
	import androidx.appcompat.app.AppCompatActivity
	import org.w3c.dom.Document
	import java.io.File
	import javax.xml.parsers.DocumentBuilderFactory
	import javax.xml.transform.TransformerFactory
	import javax.xml.transform.dom.DOMSource
	import javax.xml.transform.stream.StreamResult
	
	class MainActivity : AppCompatActivity() {
	
	    private lateinit var usernameEditText: EditText
	    private lateinit var passwordEditText: EditText
	    private lateinit var loginButton: Button
	
	    override fun onCreate(savedInstanceState: Bundle?) {
	        super.onCreate(savedInstanceState)
	        setContentView(R.layout.activity_main)
	
	        usernameEditText = findViewById(R.id.usernameEditText)
	        passwordEditText = findViewById(R.id.passwordEditText)
	        loginButton = findViewById(R.id.loginButton)
	
	        loginButton.setOnClickListener {
	            val username = usernameEditText.text.toString()
	            val password = passwordEditText.text.toString()
	
	            saveConfigFile(username, password)
	            login(username, password)
	        }
	    }
	
	    private fun saveConfigFile(username: String, password: String) {
	        val configFilePath = "config.xml"
	
	        try {
	            val configFile = File(configFilePath)
	            val xmlDoc = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument()
	
	            val rootElement = xmlDoc.createElement("root")
	            xmlDoc.appendChild(rootElement)
	
	            val usernameElement = xmlDoc.createElement("username")
	            usernameElement.appendChild(xmlDoc.createTextNode(username))
	            rootElement.appendChild(usernameElement)
	
	            val passwordElement = xmlDoc.createElement("password")
	            passwordElement.appendChild(xmlDoc.createTextNode(password))
	            rootElement.appendChild(passwordElement)
	
	            val transformer = TransformerFactory.newInstance().newTransformer()
	            val result = StreamResult(configFile)
	            val source = DOMSource(xmlDoc)
	            transformer.transform(source, result)
	        } catch (e: Exception) {
	            Toast.makeText(this, "Failed to save configuration file", Toast.LENGTH_SHORT).show()
	        }
	    }
	
	    private fun login(username: String, password: String) {
	        // Perform login logic
	        Toast.makeText(this, "Performing login with username: $username and password: $password", Toast.LENGTH_SHORT).show()
	    }
	}
	```

