Change your Twitch password, enable 2FA, and change your stream key. Right now. Do not wait.
You'll also need to reauthenticate with any third parties like Sery_Bot, StreamElements, Streamlabs, etc.
!reauth in Sery_Bot's chat or the link in thread.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko