In the App Programming Guide for iOS, Apple says:

When an app transitions to the background, the system takes a snapshot of the app’s main window, which it then presents briefly when transitioning your app back to the foreground. Before returning from your applicationDidEnterBackground: method, you should hide or obscure passwords and other sensitive personal information that might be captured as part of the snapshot.

This react-native module obscure passwords and other sensitive personal information when an app transitions to the background.

1. Run npm install react-native-privacy-snapshot --save in your project directory
2. Open your project in XCode, right click on Libraries and click Add Files to "Your Project Name"
3. Within node_modules, find react-native-privacy-snapshot and add RCTPrivacySnapshot.xcodeproj to your project.
4. Add libRTCPrivacySnapshot.a to Build Phases -> Link Binary With Libraries

let PrivacySnapshot = require('react-native-privacy-snapshot');

...

  componentWillMount() {
    PrivacySnapshot.enabled(true);
  },

  componentWillUnmount() {
    PrivacySnapshot.enabled(false);
  },