Example - 1

In the following Java example the method removeDatabase will delete the database with the name specified in the input parameter.

Statement stmt = conn.createStatement();stmt.execute("DROP DATABASE " + databaseName);try {} catch (SQLException ex) {...}public void removeDatabase(String databaseName) {}

The method in this example is declared public and therefore is exposed to any class in the application. Deleting a database should be considered a critical operation within an application and access to this potentially dangerous method should be restricted. Within Java this can be accomplished simply by declaring the method private thereby exposing it only to the enclosing class as in the following example.

Statement stmt = conn.createStatement();stmt.execute("DROP DATABASE " + databaseName);
try {} catch (SQLException ex) {...}}private void removeDatabase(String databaseName) {

Example - 2

These Android and iOS applications intercept URL loading within a WebView and perform special actions if a particular URL scheme is used, thus allowing the Javascript within the WebView to communicate with the application:

// // Android// 

writeDataToView(view, UserData);return false;
return true;if(url.substring(14,25).equalsIgnoreCase("getUserInfo")){}else{}if (url.substring(0,14).equalsIgnoreCase("examplescheme:")){}@Overridepublic boolean shouldOverrideUrlLoading(WebView view, String url){}

// // iOS// 



// // Make data available back in webview.// 
UIWebView *webView = [self writeDataToView:[URL query]];
NSString *functionString = [URL resourceSpecifier];if ([functionString hasPrefix:@"specialFunction"]){}return NO;
NSURL *URL = [exRequest URL];if ([[URL scheme] isEqualToString:@"exampleScheme"]){}return YES;-(BOOL) webView:(UIWebView *)exWebView shouldStartLoadWithRequest:(NSURLRequest *)exRequest navigationType:(UIWebViewNavigationType)exNavigationType{}

A call into native code can then be initiated by passing parameters within the URL:

window.location = examplescheme://method?parameter=value

Because the application does not check the source, a malicious website loaded within this WebView has the same access to the API as a trusted site.

Example - 3

This application uses a WebView to display websites, and creates a Javascript interface to a Java object to allow enhanced functionality on a trusted website:

super.onCreate(savedInstanceState);mainWebView = new WebView(this);mainWebView.getSettings().setJavaScriptEnabled(true);mainWebView.addJavascriptInterface(new JavaScriptInterface(), "userInfoObject");mainWebView.loadUrl("file:///android_asset/www/index.html");setContentView(mainWebView);

return currentUser.Info();JavaScriptInterface () {}public String getUserInfo() {}WebView mainWebView;public void onCreate(Bundle savedInstanceState) {}final class JavaScriptInterface {}public class WebViewGUI extends Activity {}

Before Android 4.2 all methods, including inherited ones, are exposed to Javascript when using addJavascriptInterface(). This means that a malicious website loaded within this WebView can use reflection to acquire a reference to arbitrary Java objects. This will allow the website code to perform any action the parent application is authorized to.

For example, if the application has permission to send text messages:

userInfoObject.getClass().forName('android.telephony.SmsManager').getMethod('getDefault',null).sendTextMessage(attackNumber, null, attackMessage, null, null);<script></script>

This malicious script can use the userInfoObject object to load the SmsManager object and send arbitrary text messages to any recipient.

Example - 4

After Android 4.2, only methods annotated with @JavascriptInterface are available in JavaScript, protecting usage of getClass() by default, as in this example:

return currentUser.Info();JavaScriptInterface () { }@JavascriptInterfacepublic String getUserInfo() {}final class JavaScriptInterface {}

This code is not vulnerable to the above attack, but still may expose user info to malicious pages loaded in the WebView. Even malicious iframes loaded within a trusted page may access the exposed interface:

var info = window.userInfoObject.getUserInfo();sendUserInfo(info);<script></script>

This malicious code within an iframe is able to access the interface object and steal the user's data.