Via the Rocket League Twitter page:
PC players: A small update (21 MB) was just released to address the Friends List-related stuttering issue.
Rocket League update for September 29, 2017
View all patches · Build 2157782 · Last edited August 11, 2018 – 09:06:01 UTC by 
wickedplayer494
Rumor has it:
- Size is ~25 MB