Of course it has, but it's more likely to happen when nobody is paying attention.

There's a difference between someone breaking into your house to steal your valuables, and you getting robbed after leaving your valuables on your lawn with a sign saying "Look At My Valuables"

Startups of the last decade were routinely doing this. Building their fresh ideas on the newfangled databse without bothering to investigste how to secure it in any way against malicious actors.