The company confirmed this weekend's massive leak in their first public statement.
Grand Theft Auto 6 leak

Over the weekend, the floodgates for Grand Theft Auto 6 opened whether Rockstar Games wanted them to or not. To make a long story short: Someone allegedly gained access to Rockstar Games' internal Slack system. With this access, they were able to download pre-Alpha (or thereabouts) development gameplay videos for Grand Theft Auto 6. There were over 90 videos accounting for several gigs of gameplay footage released. The hacker also allegedly gained access to at least some amount of the source code for Grand Theft Auto 5 and possibly GTA 6.

Earlier today, Rockstar Games released a public statement through Twitter. The statement acknowledges the data breach and essentially confirms that the leaked footage and other content is quite real. Rockstar's statement can be found on Twitter, but it has also been transcribed below.

A Message from Rockstar Games

We recently suffered a network intrusion in which an unauthorized third party illegally accessed and downloaded confidential information from our systems, including early development footage for the next Grand Theft Auto. At this time, we do not anticipate any disruption to our live game services nor any long-term effect on the development of our ongoing projects.

We are extremely disappointed to have any details of our next game shared with you all in this way. Our work on the next Grand Theft Auto game will continue as planned and we remain as committed as ever to delivering an experience to you, our players, that truly exceeds your expectations. We will update everyone again soon and, of course, will properly introduce you to this next game when it is ready. We want to thank everyone for their ongoing support through this situation.

- The Rockstar Games Team
The reception to the leak has truly been something to behold. There are people who understand how game development works and understand that what they're looking at is very much pre-Alpha in-development footage that is far from complete. Then you have the people who are livid that the game looks "so bad." Still others are saying that Rockstar Games (and other development studios) "deserve this" because they chose not to officially reveal their unfinished game yet. Of course, we also cannot forget the group that are complaining about having to play as a woman while also simultaneously shouting "go woke, go broke" everywhere.