It seems there's suspiciously little context available, yet here I also am commenting on a 'vaguepost'. I wonder if one day AI will be able to filter out vagueposts from my browser along with ragebait and curiosity gap headlines.
My guess is that Adafruit tried flux.ai, noticed a server misconfiguration, contacted flux about it, and then received a cease and desist to prevent them disclosing the vulnerability publicly.
(AFAICT they haven't published anything yet? If they have it's been taken down).
There's a definite bit of Streisand effect here because I for one am very much looking forward to finding out what the deal is.
Best I can tell they've taken down whatever it was, but most likely flux left some ways to get data out of their system that shouldn't have been and Adafruit leveraged that. Could have been in a good way like exposing false claims of architecture or security, or a bad way like revealing proprietary information on how the platform worked or looking at other peoples' projects (more than just seeing they could do that). If the blog doesn't come back up, I'll kinda assume they did something bad. I don't have sources but I've heard adafruit isn't the sweetest fruit in the tree...