Supposedly Citron got out of their short somehow, either they bought enough options to cover their short (which would be incredibly expensive) or had the ability to cancel their contract. The people at WSB last I checked think this is a bluff and it's not actually true, and that they still need to buy more than 100% of the shares in circulation on Friday, and so that any stock you still have can be sold on Friday for a higher price than it is currently being sold for, as they will have to buy all stock in circulation more than once putting immense pressure on the stock to go up. I don't know if that is true, that's just a claim I read on WSB.
Alternatively Gamestop could put a stop to this buy selling enough the companies own stock to to allow the shorts to liquidate, they would be able to raise an immense amount of capital. Alternatively they may not do this so that anyone shorting them eats a huge loss, and has a big incentive not to try to short in the future.
In general for people not aware, publicly traded companies are usually given the ability issue a certain number of shares that is far bigger than the amount they actually issue. So at any time they could decide "lets raise some funds" and start issuing new shares.
I'm not sure how exactly they know how many shorts are out there, but people on the subbreddit were saying earlier today that the stock was still being shorted, and that there are actually more shorts out there now than there were on Monday. I have no idea if this is true, I've rarely looked at shorts, and have no idea how you get information on this. This isn't the kind of investing/speculation that I do.
Personally I'm not touching the stock. I've never studied short squeezes before, and if I don't understand something when it comes to investments my instinct is to sit on the sidelines and watch.