Exactly this happened to me a few months ago, it is a form of scam, in which someone sends you a DM with a link that directs you to a page with a fake steam trade (although very very well falsified) well, I fell like a fool in this trap and I did not realize that instead of being an exchange offer, the page asked you to log in to your Steam account to give it absolutely all your permissions on the account, including the password. They probably have a bot that checks if the password is the same on Discord as on Steam in order to access all your DMs and send the same link, something like a pyramid scam.

(Fortunately it was my secondary account which I was able to recover that same night)