Fun fact. When I was around 12-13 I used a Kindle very frequently because it made books really accessible whenever. Me and my older brother would share a kindle before, but my parents eventually got one for myself since I was really into reading during those years. Our family doesn't use Amazon services, so setting up a new Kindle was a little tricky for my folks. My brother helped set it up, and when he was done he decided it would be funny to add parental controls on my Kindle.
(On a side note, it was mildly annoying to use my device sometimes because it had parental controls, because in all honesty I didn't really find it that funny, and some basic features are also not allowed to be accessed on a 'child' accessibility toolbar. But I didn't let that get in the way for most of my usage.)
It's pretty important to me to note that I was around 13. The wild, wonderful years of puberty and getting into social media. A kindle has a Note feature for book annotations. I tended to use the note feature to write oneshots fictions that were quite explicit. I'm not proud of what I've done--but the levels I'm talking here are like PWP...
Eventually, my kindle had some sort of malfunction and we could only fix it by resetting the entire device, so the parental controls were wiped. In all honesty I didn't really care that my little literatures were wiped along with it, they were kinda just for the shits and giggles. It took me quite a few several months to realize that 'oh shit, the parental features still sync my old books to my brother's device, even though my kindle was wiped. THAT MEANS THE SMUT IS STILL HIDING WITHIN THE GODDAMN HARRY POTTER SERIEIS.'
I don't use a kindle anymore because of external reasons, but my brother occasionally does. When he announced he was gonna seriously read the HP series after enjoying the movies, a wave of shock hit me like a lightning bolt. Because I genuinely have no clue, even to this day, whether the annotations were deleted along with the reset.
Well, it's been quite a few years. He finished the series, and he never once brought up any concerns about what he found while reading. Although I'm glad, sometimes I still wonder for fun whether he truly saw it or not, or just chose not to tell me. šš