Hacker News Reader

I know of two instances:

1) Facebook had a "View as" bug that allowed anyone to view anyone else's private page as that person.

2) Cambridge Analytica in which Facebook shared private information with third-parties under an NDA.

As I recall, the 'View As' was a feature, allowing you to see your own profile and posts as would be seen by another person, so you could make sure your post privacy/visibility settings were set up the way you wanted. I used the feature quite often and was quite annoyed when they disappeared it one day. Do you have more info on this?

Here's some info on the View As bug posted by Facebook:

https://about.fb.com/news/2018/09/security-update/

Reply on news.ycombinator.com