Comment 75 for bug 372103

(In reply to comment #33)
> Anyway, selection_data and its description by atoms is created by application
> which pastes data into clipboard. Mozilla has not any mechanism how to deny
> third-party app to paste incorrect targets into clipboard. We can only ignore
> them.

Yes, another app may put anything into the X Selection.

But gtk_selection_data_get_targets() should return GdkAtoms.
GdkAtom is a type specific to GDK and has no meaning for other apps.
GdkAtoms should not come (directly) from another app, so I filed

https://bugzilla.gnome.org/show_bug.cgi?id=601611

The comment "As usual, java gets it wrong and sets the type to TARGETS, not ATOM" in gtk_selection_data_get_targets() was helpful.