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 3.11.7.This latest update for GTK is somewhat smaller, mostly because the developers are approaching the final version. This is the branch that will eventually evolve into GTK+ 3.12 stable.
Highlights of GTK+ 3.11.7:
• The theming for the GtkActionBar has been fixed;
• A size-allocation error has been fixed;
• The new xdg-shell ping for Wayland is now used;
• A small memory leak has been corrected.
A complete changelog featuring all the updates and fixes can be found in the official announcement. Download GTK+ 3.11.7 right now from Softpedia.
Remember that this is a development version and it should NOT be installed on production machines. It is intended for testing purposes only.