Comment 19 for bug 1272001

Manually patching this issue -- under the "Text Entry" Section, the background for the .entry class must also be added:

(extending pato101's suggested fix):
###########################################################

GtkWindow {
     color: @theme_fg_color;
     background-color: @theme_bg_color;
 }
GtkPaned {
     color: @theme_fg_color;
     background-color: @theme_bg_color;
 }
.entry {
    background-color: @theme_bg_color;
}

###########################################################

Freya (EOS) Users can use the attached .css file to replace their vanilla version stylesheet at /usr/share/themes/elementary/gtk-3.0/gtk-widgets.css

Cheers