So, not long ago, I reinstalled the Sigma hacked client.
I like the design of Jello and more specifically the in-built music player, and just the general look and how clean it is. I played on it for 2-3 days and prior to this, I used no in-game modifications apart from the bog-standard optifine. That was all fine until recently I was playing on a private server with @venomsx and he pointed out to me that my skin had changed, and that he liked it.
So I logged onto hypixel, only to hastily get kicked for being logged in from another location. I got a little glimpse, and it looked like I was in the middle of a game of bedwars. I eventually got in and realized I was in a party. I decided to chat to the guys in the party and ask them questions and here's how that went
I soon came to realize that Sigma had grabbed my login data, and sold it off to some alts website. Luckily the guys were nice enough & didn't actually hack on my account but I reckon that was more luck of the draw rather than anything else.
So yeah, TL;DR, don't use Sigma, and if you are, don't use an account you care about on it.