Via [url=https://store.steampowered.com/news/55155/]the Steam store[/url]:

[quote=Valve]- Updated the Accursed Unusual taunt effect to fix a problem with the color
- Updated the equip_region for a couple of the Spooky Spoils cosmetic items
- Updated/Added some tournament medals
- Updated the localization files
- Updated koth_slaughter_event
- Fixed a spot where players could spam the Underworld exit effect
- Fixed a sightline into the spawn rooms
- Fixed players being able to perch on flood lights
- Implemented additional prop fades to increase performance
- Updated pl_precipice_event_final
- Removed the right side path from BLU spawn near control point A to help BLU in keep momentum during coordinated pushes
- BLU main spawn has been rearranged to outlet the BLU team to the left of the courtyard
- Removed upper balcony for control point D on the RED team's side
- Added additional cover near control point A and control point D to block long headshot sightlines
- Redesigned RED spawn to support missing balcony level
- Added a ramp inside the Cave to allow players to jump up onto the dropdown platform that leads to control point D
- Fixed engineers being able to build in certain doorways
- Moved the health cabinet in the neutral spawn closer to the exit doors
- Fixed one-way doors closing too soon, trapping players
- Fixed the cliff-side one way door not closing properly, leaving behind invisible collision
- Added additional health and ammo pickups between control point A and control point C
- Fixed several spots players shouldn't be able to reach
- Extended spawn room triggers to better encapsulate the neutral forward spawn room
- Made several shed rooftops non-buildable areas for engineers
- Added more pumpkin bombs
- Spells cast by the cauldron are now helpful for the BLU team. The cauldron will only cast the tornado, jump pad, and skeleton spell. Skeletons will target and attack RED team.
- Fixed the cauldron spell audio not always playing correctly[/quote]

Rumor has it:

- Localization file updates and tournament medal additions can be scrolled through here: https://github.com/SteamDatabase/GameTracking-TF2/commit/bce85bbe982ca966ea9cf5f3befb4a730476cb68

- Size is ~60 MB