This one adds another scenario that can be seeded in a nebula. The usual goes with it: more champion hulls and module lines are possible as rewards. There's also a couple new abilities that can be unlocked through nebula rewards.
A few important balance changes were made to recently-added stuff: Tackle Drone Launchers got nerfed heavily. Scapegoats got something of a nerf, but the higher-mark versions now actually deliver more of their unique utility than the first mark, rather than less.
Also added keybinds to make champion direct-ability-use easier, now that it's a thing. Basically Ctrl+Q to use your first ability, Ctrl+W to use your second, and so on, though you can only get 2 on any one champion right now. If you prefer the Q,W,E,R (without holding Ctrl) method, you can change the binding and it will only apply when you have a single champion selected so it won't interfere with the normal zoom-functions of those keys at any other time.
There's also a few other miscellaneous changes and fixes, as usual.
Update: 5.069 hotfix is out to fix a bug where only the most-recently-added scenario was being seeded in nebulae. What do you mean, "did you leave testing code in, Keith?" Have I ever done such a thing? ... um, yea. Anyway, a few other important fixes in there (like preventing minor-faction ships with plasma-siege shots from "helpfully" killing forcefield-protected AI command stations for you) and a long-needed buff to CPAs on higher difficulties, though we probably aren't done on that front.
This is a standard update that you can download through the in-game updater itself, if you already have 4.000 or later. When you launch the game, you'll see the notice of the update having been found if you're connected to the Internet at the time. If you don't have 4.000 or later, you can download that here.