Via [url=https://steamcommunity.com/games/CSGO/announcements/detail/498333631688736879]the Steam Community[/url]:

[quote=Valve][b][u]MAPS[/u][/b]
[b]Ancient[/b]
- Various player clipping fixes

[b]Train[/b]
- Various player clipping fixes

[b][u]MISC[/u][/b]
- Fixed a case where you couldn't start moving while wiggling the mouse.
- Fixed a case where velocity was abnormally low while walking up ramps.[/quote]

Rumor has it:

- Size is just over 1 GB (with Workshop Tools installed)