Via HLDS and [url=https://steamcommunity.com/games/TF2/announcements/detail/3703707247834610958]the Steam Community[/url]:

[quote=Valve]- Added an extra HIDEHUD flag for vscript maps (HIDEHUD_TARGET_ID)
- Fixed using the extendfreeze client command to continue spectating enemy players after being killed
- Fixed Arena mode player count HUD layout problem (community fix from Funicular)
- Updated zi_atoll to sync the particles file with other the Zombie Infection maps

- Updated zi_woods
- Added props to aid scouts in getting up to the roof on the boathouse
- Added trigger_push entities to the tops of trees
- Implemented an optimisation pass

- Updated koth_sawmill_event
- Added spells to the Underworld Forest to encourage players to travel there
- Added trigger_hurts to prevent spawn camping in the Underworld Forest
- Added the Skeleton King to randomly spawn after cap
- Added an additional Skeleton Consort for him as well
- Reduced the amount of particles in the Underworld Harvest
- Removed a custom texture since it wasn't needed
- Minor clipping changes
- Added an ammo pack to the cave
- Removed a few pumpkin bombs since they hurt player movement too much
- Added a loss-coverage program for Red team
- Cleaned up some waste[/quote]

Rumor has it:

- Size is ~55 MB