### HTML Injection

HTML injection is a security vulnerability that occurs when user-manipulated input in a mobile application can be used to insert arbitrary HTML code into a vulnerable webview. This vulnerability can be exploited to launch various attacks, such as stealing a user's session tokens or CSRF tokens, which can then be used for further malicious activities. Additionally, it allows attackers to modify the content displayed to victims, giving them the ability to insert malicious code or deface the page with their own message.

**Code Examples:**

- Dart
```dart
import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'HTML Injection Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: WebViewScreen(),
    );
  }
}

class WebViewScreen extends StatefulWidget {
  @override
  _WebViewScreenState createState() => _WebViewScreenState();
}

class _WebViewScreenState extends State<WebViewScreen> {
  late WebViewController _webViewController;
  String? htmlInput;

  @override
  void initState() {
    super.initState();
    getHtmlInputFromIntent();
  }

  void getHtmlInputFromIntent() {
    // Retrieve the intent extras
    Map<String, dynamic>? extras = ModalRoute.of(context)?.settings.arguments as Map<String, dynamic>?;

    // Extract the user input from the intent extras
    htmlInput = extras?['htmlInput'];
  }

  void _injectHtml() async {
    if (htmlInput != null) {
      await _webViewController.loadUrl(Uri.dataFromString(htmlInput!, mimeType: 'text/html').toString());
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('HTML Injection Demo'),
      ),
      body: Column(
        children: [
          ElevatedButton(
            onPressed: _injectHtml,
            child: Text('Inject HTML'),
          ),
          Expanded(
            child: WebView(
              initialUrl: 'about:blank',
              onWebViewCreated: (WebViewController controller) {
                _webViewController = controller;
              },
            ),
          ),
        ],
      ),
    );
  }
}
```

- Kotlin:
```kotlin
import android.annotation.SuppressLint
import android.os.Bundle
import android.webkit.WebSettings
import android.webkit.WebView
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    private lateinit var webView: WebView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        webView = findViewById(R.id.webView)

        val name = intent.getStringExtra("name")

        val html = "<html><body><h1>Hello, $name!</h1></body></html>"
        webView.loadDataWithBaseURL(null, html, "text/html", "UTF-8", null)

        val webSettings: WebSettings = webView.settings
        webSettings.javaScriptEnabled = false
    }
}
```

- Swift:
```swift
import UIKit
import WebKit

class ViewController: UIViewController, WKNavigationDelegate {

    var webView: WKWebView!
    var htmlInput: String?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Retrieve the user input from the intent extras
        if let extras = self.navigationController?.navigationBar.accessibilityUserInputLabels {
            htmlInput = extras["htmlInput"] as? String
        }

        // Create and configure the web view
        webView = WKWebView(frame: view.bounds)
        webView.navigationDelegate = self
        view.addSubview(webView)

        // Load the web page
        let htmlString = "<html><body><h1>\(htmlInput ?? "")</h1></body></html>"
        webView.loadHTMLString(htmlString, baseURL: nil)
    }
}
```
