I remember when I was ~14 at a private day school with a 1:1 laptop program in the early 00s, we were on AD. There was essentially one mac user in the IT department and the rest was windows, and inadvertently his mac created a hidden folder, I think it was "FindByContent" or something, that allowed full permission to all users in AD. Kids quickly noticed this, made a new AD group that was just us and locked it down a bit more, and for years interesting things started building up in that directory, pirated games (halo 1 for pc), artwork, test answers, even some porn if I remember correctly. Years later I worked for two years in that IT department and it was still there, with a whole decade of built-up content. We decommissioned it but it was super interesting to see how it had been used over the years.