tl;dr: Google chrome has a timing attack with :visited css selector. Adapt the PoC from [WONTFIXed chrome bug report](https://bugs.chromium.org/p/chromium/issues/detail?id=252165#c2) to find the the report a link bot's browser history.

Original writeup (http://bawolff.blogspot.com/2021/10/write-up-pbctf-2021-vault.html).