The Oppo F5 Android device with a build fingerprint of…

Summary

The Oppo F5 Android device with a build fingerprint of OPPO/CPH1723/CPH1723:7.1.1/N6F26Q/1513597833:user/release-keys contains a pre-installed platform app with a package name of com.dropboxchmod (versionCode=1, versionName=1.0) that contains an exported service named com.dropboxchmod.DropboxChmodService that allows any app co-located on the device to supply arbitrary commands to be executed as the system user. This app cannot be disabled by the user and the attack can be performed by a zero-permission app. Executing commands as system user can allow a third-party app to video record the user's screen, factory reset the device, obtain the user's notifications, read the logcat logs, inject events in the Graphical User Interface (GUI), and obtains the user's text messages, and more. This vulnerability can also be used to secretly record audio of the user without their awareness on the Oppo F5 device. The pre-installed com.oppo.engineermode app (versionCode=25, versionName=V1.01) has an exported activity that can be started to initiate a recording and quickly dismissed. The activity can be started in a way that the user will not be able to see the app in the recent apps list. The resulting audio amr file can be copied from a location on internal storage using the arbitrary command execution as system user vulnerability. Executing commands as system user can allow a third-party app to factory reset the device, obtain the user's notifications, read the logcat logs, inject events in the Graphical User Interface (GUI), change the default Input Method Editor (IME) (e.g., keyboard) with one contained within the attacking app that contains keylogging functionality, obtain the user's text messages, and more.