Yes, it auto-updated, although I can't see the new changelog. Could be that I'm mistaken, and it's an earlier patch. My version is currently 1.5.29823-REL-DEV-ST.
Ah, so it is the newest update. The offline installers are still at 1.4
Here the changelog if you haven't seen it yet:
1. Optimization improved in many respects, most noticeably:
lowered the amount of RAM used;
lowered freeze frequency;
improved average FPS;
lowered CPU usage.
2. Headshots added!
3. Gamepad support added.
4. Game logic polished, fixed a number of smaller bugs.