The breach in question is documented here: https://youtube.com/watch?v=lUiLBBab1RY
I don’t think there’s a text write-up, but tl;dw a combination of missing input sanitization and no-code UI trickery made it possible to leak other users’ bot tokens, and despite patching the exploit pretty quickly on exposure, BotGhost’s developer tried to cover it up and refused to reset potentially affected tokens.