Rating:

Deaddrop was a HTTP service written in Erlang. It models a simple bulletin board system, where users can create topics and reply to them. Topics can either be public or private (where users have to know their name to access them). Two logical flaws and a path traversal-like vulnerability allow attackers to list the private topics and steal data.

tl;dr:
1. Replay `- topics`
2. Publish `topics` to `- topics`
3. Create and replay topic `./topics`

Original writeup (https://saarsec.rocks/2019/07/12/deaddrop.html).