Via [url=http://blog.counter-strike.net/index.php/2018/12/21577/]the CS:GO blog[/url]:

[quote=Valve][ RENDERING ]
– [b]Fixed graphics regression that caused smoke and molotov particle effects to appear fully transparent.[/b]
– [b]Fixed client crash on startup on Intel GPUs.[/b]
– New users now default to Borderless Windowed mode.

[ GAMEPLAY ]
– Fixed ‘self-boost’ movement regression.
– Fixed players not respawning on round restart if they were in the middle of jumping up onto a platform that would force them to duck.
– Fixed bullet penetration damage regression.
– Fixed molotov not detonating in mid air in non DZ modes.

[ CS:GODZ ]
– The winner of the match now watches their victory from the perspective of the runner up.
– In duo and trio matches teammates are now notified with an onscreen alert if one of them dies.
– Adjusted–and added volume slider for–winner music.
– Recent Teammates now shows teammates from Danger Zone matches.
– Players searching count now shows correct number of people searching for Danger Zone matches.[/quote]

Rumor has it:

- Most of the size of this update [url=https://github.com/SteamDatabase/GameTracking-CSGO/commit/074bb8402ebcab2138455b3b5418c6c7ee8d947a#diff-d876b985855609ae8ed36ffe97547ad8R16888]is in model and texture updates[/url] for the helicopters and supply boxes

- Semi-related to this update, it appears the new Steam Datagram system infrastructure hosted on Google's Cloud Platform [url=https://steamdb.info/app/730/history/?changeid=5521912]will be getting some use in CS:GO[/url]

- A few SDR-related protobufs [url=https://github.com/SteamDatabase/Protobufs/commit/da54574fde7c7589d69427537684dcf6efe86195]have also been marked as legacy[/url]

- [url=https://github.com/SteamDatabase/GameTracking-CSGO/commit/074bb8402ebcab2138455b3b5418c6c7ee8d947a#diff-2376c954aec3534dcd1d16ff16959553R20235]There will also be a few new clusters[/url], 3 of which are likely to be GCP clusters in US West, Germany, and Hong Kong, as well as 4 others that are yet to be determined ([i]Winnipeg as "Canada Central" shilling intensifies[/i])

- Size is ~20 MB

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[b][url=https://support.steampowered.com/kb_article.php?ref=1558-AFCM-4577]Valve will end its support of Steam on Windows XP and Windows Vista in 1 month, on 1/1/19.[/url][/b] Any future CS:GO updates that moves the minimum Steam client version beyond the last one available for XP/Vista will render it unplayable unless you upgrade Windows.