In their blog post, Valve pointed towards an increase in the usage of CS:GO keys by “worldwide fraud networks” to liquidate their gains as the reason for the change. The blog post went on to say that “at this point, nearly all key purchases that end up being traded or sold on the marketplace are believed to be fraud-sourced.”
The change to the trading and selling of keys will only effect newly purchased keys, meaning that any keys that already exist in inventories or on the market will remain unaffected.
The update also fixed a client UI issue as well as an exploit in Danger Zone that allowed for players to avoid damage if they had an invalid name.
You can find the full 10/29/2019 update patch notes below:
[ MISC ]
– Added restrictions on tradability and marketability of newly purchased case keys, see here for more details.
– Fixed a client UI issue sometimes displaying CS:GO Weapon Case as genuine quality.
[ DANGER ZONE ]
– Fixed an exploit where players could avoid Danger Zone damage if they had an invalid player name.
– Once a drone starts self-destructing it can no longer grab cargo.