These are the changes of ARK: Survival Evolved’s Patch 185.3, grouped into categories for clarity. If not otherwise indicated, they’re quoted from the relevant Steam Thread.

UI Changes

• Server Passwords now appear as Asteriks’ in Admin Managment UI (soon you’ll be able to change this dynamically via the UI), and “message-of-the-day changing in the UI” crash is fixed

Bugfixes

• Fixed various mods crashing — any which used custom Materials, such as Apako Island: http://steamcommunity.com/sharedfiles/filedetails/?id=469987622&searchtext=
• Fixed a Chatbox crash
• Eliminated some Snapshot_16 “permanent” hangs if banned or missing communication from server during connection

Performance

• Improved speed of background loading core game data while at main menu

(Original Announcement on Steam)

Here are the patchnotes of the previous patch (185.2)