just got a used roadbike, it has full carbon forks, apart from the dropouts (which are aluminium i spose?).

just noticed that the metal of the dropouts has this thick laquer, and some of it has loosened allowing moisture in and this white stuff to build up.

is it corrosion, is it bad, do i need new forks?

It's fine.

Just the alloy oxidising a little.

If you're worried about the looks, you could strip the lacquer off and polish it up with Autosol. Problem then is that you have to keep doing it.

That's superficial and will clean off. You could try re coating it with auto lacquer. Halfrauds have it with the touch up sprays or support your local independent car part shop.