Via [url=http://blog.counter-strike.net/index.php/2018/05/20417/]the CS:GO blog[/url]:

[quote=Valve][MISC]
– Bomb logic now runs every tick when it is close to exploding or being defused, addressing some rare cases where an extremely close defuse would still result in the bomb exploding.
– If a bomb would both explode and be defused at the same exact time, it will now be considered defused.
– Prime accounts will now receive a warning in a Competitive lobby when they enter matchmaking with other Prime accounts whose Trust Factor may impact their matchmaking experience.

[GAMEPLAY]
– General adjustments to ambient sounds:
— Increased resolution and character of reverb effects to better reflect surrounding map geometry
— Small mix adjustments
– Improved vent destruction sounds and increased audible distance.
– Added a new hitbox type for necks and applied it to the existing neck hitbox on character models. Bullets that penetrate the neck into the head will now count as headshots. This should make it more intuitive to tell when an attack from behind will result in a headshot.
– Fixed ‘use’ key to more reliably pick up weapons on the ground and to not drop the active weapon if a replacement weapon cannot be picked up.

[MAPS]
Nuke:
– Optimizations for low settings
– Blocked visibility between silos inside A site
– Ported over ShortNuke gameplay changes:
– Removed Toxic
– Vent no longer connects directly to B site, but has another exit close to double doors
– Pushed new corner boxes on B site further back to prevent headshot angle towards ramp
– Added solid background to yellow crane inside B site
– Smoothed out some player movement

Overpass:
– Lowered volume of ambient sounds in Overpass
– Added grenade and player collision to fence cage near construction
– Removed spooky shadow fading in when approaching T main entrance to B site[/quote]

Rumor has it:

- /u/kkthxbye- says that [url=https://www.reddit.com/r/GlobalOffensive/comments/8l42ev/counterstrike_global_offensive_update_for_52118/dzcpzuz/]several exploitable cvars are now protected by sv_cheats after a bug report to Valve[/url]

- [b]Wondering "what is this Trust Factor thing"? [url=http://blog.counter-strike.net/index.php/the-trust-factor/]You can read about The Trust Factor system and how it works on the CS:GO website[/url][/b]

- The warnings for lower trust factors read as follows ("%s1" being the player in your party with the lower trust):
- For a slight impact: "Your matchmaking experience may be slightly impacted because the Trust Factor of %s1 is lower than yours."
- For a significant impact: "Your matchmaking experience will be significantly affected because the Trust Factor of %s1 is substantially lower than yours."
- And at the end of each: "CS:GO's matchmaking will prioritize finding opponents with a similar substantially lower Trust Factor."
- [url=https://i.imgur.com/nN5ihrX.jpg]It'll appear as a red warning notice in chat[/url] just like if someone was responsible for being that 10th player to not click ready ([url=https://www.reddit.com/r/GlobalOffensive/comments/8l42ev/counterstrike_global_offensive_update_for_52118/dzcp2qi/)]screenshot courtesy of /u/master117jogi[/url])

- Remember MaxReiger's [url=https://www.reddit.com/r/GlobalOffensive/comments/7jm1s3/the_unnoticed_patch_update_part_65survival_island/]leak of an unreleased "survival_island" map?[/url] It seems that the soundscape file for it [url=https://github.com/SteamDatabase/GameTracking-CSGO/commit/7dafc8004ebe57d4dd3cae1737aa14ac03616588#diff-ee7bb480334d4a64990353395fbee1b2L100]has been added to the manifests file in today's update[/url], but it's entirely possible that it may disappear in the next update or be left otherwise untouched for a long while

- You can view the script changes for the various sound changes and everything else [url=https://github.com/SteamDatabase/GameTracking-CSGO/commit/7dafc8004ebe57d4dd3cae1737aa14ac03616588]over here[/url] - but as DavidWValve said a few days ago, use caution when attempting to infer anything through these config files

- If you're intending on reporting issues, particularly issues with game performance, and you happen to be on Windows 10, please make mention of whether or not you're on Redstone 4/the "April 2018 Update" as not all issues may be caused by this update itself (or the previous one), but by Redstone 4
- Unsure of whether or not you're on Redstone 4? Search for "winver", and if "OS Version" is 1803, you're on Redstone 4. Otherwise, if it says 1709, you're still on Redstone 3
- I'll leave this notice out by mid-June as most Redstone 4-related issues should have been ironed out by then, either by Microsoft or by you

- Size is ~85 MB