Researchers identified some two dozen Tor nodes that were attempting to subvert the Tor network.
The official Tor blog has a post on this further clarifying how this data should be interpreted: https://blog.torproject.org/blog/what-spoiled-onions-paper-means-tor-users
I’ve always been weary of exit nodes. I wish that more companies would instead run a hidden service for the their website. They’re so easy to setup and offer much better security (as the traffic never leaves the Tor network).