running this in the current (jan 2017) fedora25 in gnome-shell (wayland mode). also tried in weston.
with the xwayland module loaded, any app can see any clipboard by calling x11.
to see this, run 'watch xsel -b' in a terminal, and copy to the clipboard from any wayland app.
can this be changed so the x clients can only see the clipboard after getting focus? this is especially important for password keepers.
I think this probably needs to be fixed in the Xwayland clipboard integration code in each compositor. It probably won't be possible to fix for X11<->X11 clients, as they talk with each other directly, but we could probably stick some branches in the wheel when X11 clients tries to steal clipboard content when a Wayland client is focused.
Per Jonas's comment, closing this here so it can be tracked everywhere it happens.