I have not said that someone does it manually, I only said, that on first look, that looks really suspicious. And, at the end, the support told me that:

"This is Kamal Nasser's script that has been set up to run on the images. The cleanimage.sh script sometimes doesn't clear the history. Thank you for bringing this to our attention. I've brought this to his attention.

There is nothing to worry about with this."

So in fact, it seems like it is being used, instead of being a leftover in shell history. In addition to that, I was later answered to the same ticket, by different support member that this script is not being used and just sits on that web page, but it all looks really bad in terms of professionalism.

Agreed. I wasn't defending DO's professionalism there, just saying that from my experience creating base images for a (different) cloud provider, it looks like an artifact of image creation rather than a real cause for alarm (I would certainly be alarmed if random people were logging in to my instance and running random scripts from the web!).

Yah, that's sloppy and won't happen again. Sorry you had that experience.