To mitigate XML injection vulnerabilities, it is crucial to 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. Additionally, 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()
	    }
	}
	```

