I created Sharesecret (https://sharesecret.co) to protect against exactly these kinds of attacks.
Most company Slacks are a ticking timebomb of sensitive artifacts waiting to be discovered. Whether it's passwords or just general internal info you wouldn't want to be public, it's wild how much sensitive info is sitting in like 4 systems (Slack, Gmail, Notion, Dropbox).
Protect y'selves people.