The engineer technically was an end user. It was a service that could get called as an indirect result of customer action, but without any customer supplied information passed along, which is part of the reason it didn't do any input clean-up (at least according to the post-incident report). They assumed they could trust people not to screw things up.

To be fair, it had been running for a long time that way without anyone doing that to them.

All good, I hope my comment didn't come off as snarky because I have 110% been in similar environments!