I agree, but in fairness, I don't know of any brand, tech or otherwise, that can completely wall itself off against insider threats. No matter how vigilant you are, someone who knows exactly how you move will find a way around you.
You'd be surprised how many websites use Google Tag Manager to allow their marketing department to roll out trackers and other JS snippet directly into the site's root context.
GTM et al's sole reason of existence is to provide marketing people with a way to bypass corporate IT.
And I definitely would not rule out something like this being the cause in the end.
Humans reading code is so "legacy"...