Worse: back in the day, you could type raw HTML into AOL Instant Messenger. Notably, being able to construct a link with whatever address you pleased, including `file://c:\con\con`.
Not just that, AOL allowed playing sound files from within a chat room. If a user sent `{s gotmail`, it would play the `gotmail.wav` file on the computer of each person currently in the chat room. So, sending `{s /con/con` or `{s /aux/aux` to that chat would instantly crash the computer of everyone in the chat, causing a BSoD. It was great fun if you were an obnoxious kid, and generally super frustrating for anyone trying to chat.
There was something similar with popular irc clients on windows in the late 90s early 2000s. There was a direct file transfer mechanism called dcc. If you forged a request for con/aux device files you could send instructions to the person's printer or modem and do all sorts of interesting mischief.