Title.
I can think in any sort of DoS or someone spamming messages to increased the billing.
Any idea?
Look into google but I cant find anything.
Yes it is, at least if it includes the keys. Spamming messages to increase the bill would be the least of my worries. Say someone reads all the incoming messages, could be a potential security issue. Or consider someone sending rogue messages, causing all kinds of trouble. Good luck finding out that bug.
Also, exposing any information regarding the azure infrastructure in use to parties not needing to know would be a no-go for me personally.