This is a bit click-bait-y. Mongo gets a lot of flack, but this really applies to any database.
- I wrote about it before and could compare results from my previous post
- It's popular and there are a lot of public instances of it
- MacKeeper exposed 13 million user accounts through their public MongoDB instance
And I actually wrote a follow-up post on Memcached to highlight the same issue: https://blog.shodan.io/memory-as-a-service/
Also, the author stresses that this problem is not unique to mongo.