Comment 1 for bug 1366314

It does seem that the keyboard shouldn't be putting whatever you type into the clipboard.

That said, I wonder if this is also a bug in the terminal app? Maybe it isn't using these:
Qt.ImhHiddenText - Characters should be hidden, as is typically used when entering passwords. This is automatically set when setting echoMode to TextInput.Password.
Qt.ImhSensitiveData - Typed text should not be stored by the active input method in any persistent storage like predictive user dictionary.

Note, AIUI, the filemanager app uses the same embedded password checking backend as the terminal so it may be affected too.

Reference:
http://people.canonical.com/~dpm/sdk-docs/html.orig/qml-ubuntu-components0-textfield.html