Android Logcat is an internal logging buffer, where apps write debug or error information. It is also a place where apps may leak personal or sensitive information. Even though the security situation has improved since Android 4.1, in that not all apps may read from Logcat, apps may still do so on rooted devices or you may access logcat via the ADB / USB debugging connection. And, of course, the Android OS itself has access to these logs.
Take Firefox Klar, a privacy browser, which still logs information about pages you visit into the Android Logcat file. App Cloner 1.5.2 comes with a new privacy modding option Disable Logcat logging that disables all output to the Android Logcat at both Java and C/C++ native levels.
See screenshots before and after done with the Logcat viewer option.