Via the CS:GO blog:

MISC

• Fixed quad surround sound so it works again.
• Fixed a bug that could cause looping sounds, such as the hostage breathing sound, to be stuck on in some situations.
• Fixed a rare bug that caused spectators to sometimes hear water footsteps coming from players on dry ground.
• CS:GO items received in trade cannot be re-traded for seven days.

SDK

• Added support for uniform scale adjustment of static prop models.
  • To re-size static props, adjust the “uniform scale override” prop_static Hammer property, or use shift mousewheel in the Hammer 3d viewport.

MAPS

Nuke:

• Moved squeaky door back a bit, to give a clearer view towards hut
• Changed geometry near crane when on rafters, to remove awkward position
• Smoothed out movement on roof near T spawn
• Changed color of new boxes in bombsite B
• Changed color of small red box at T side of yard
• Added some cover at back of squeaky door hall

Dust II:

• Removed one-way wallbang from CT spawn up to cat
• Fixed some minor bugs
• Fix for mip bias exploit

Canals:

• Opened up B lobby to stairs
• Simplified geometry around B site for better movement
• Blocked “invisible” area at A
• Fixed several “pixelwalking” exploits
• Fixed various minor bugs

Rumor has it:

• There's a blog post on the new trade restriction: http://blog.counter-strike.net/index.php/2018/03/20308/

• There's also a healthy dose of localization

• Size is ~130 MB