"Companies often have a demo environment that is open" - huh?
And... Margolis allowed this open demo environment to connect to their ENTIRE Box drive of millions of super sensitive documents?
HUH???!
Before you get to the terrible security practices of the vendor, you have to place a massive amount of blame on the IT team of Margolis for allowing the above.
No amount of AI hype excuses that kind of professional misjudgement.
I don't think we have enough information to conclude exactly what happened. But my read is the researcher was looking for demo.filevine.com and found margolis.filevine.com instead. The implication is that many other customers may have been vulnerable in the same way.