The latest version of GTK+ can be downloaded from Softpedia
GTK+, a multi-platform toolkit for creating graphical user interfaces that provide a complete set of widgets, suitable for projects ranging from small one-off tools to complete application suites, is now at version 3.12.2.This latest update for GTK is not one of the largest, but it does cover some important changes that have missed the previous two versions in the new 3.12.x branch. The new GTK arrived along with GNOME 3.12 and the two projects are closely related. This means that all the GTK+ updates are usually pretty important.
According to the changelog, the Open recent file keyboard shortcut is now working properly, a number of problems with CSDed windows have been corrected, the color picker check marks are now cleared properly, a missing transfer annotation has been added to gtk_box_get_center_widget, and drag and drop (GdkFrameClock) now works for hidden widgets.
Also, the broadway backend build on OpenBSD is now working, some graphics artifact that occurred when scrolling with the hover-selection has been fixed, and a weird black border that appeared when the user was dragging file has been fixed.
A complete changelog featuring all the updates and fixes can be found in the official announcement. You can download the GTK+ 3.12.2 sources right now from Softpedia.