Valve had to remove one of the heroes from Dota 2 matchmaking

Valve has disabled the option for players to choose the Lone Druid hero in Dota 2 matchmaking as a result of an error that game server may be crashed by any player upon selecting the character.

Somebody posted instructions on how to make it happen on Reddit.

"Hello everyone, I want Valve to fix the server crash as soon as possible, so I'll explain how the bug works.

1. You need any neutral item with a cooldown.

2. Transfer it to the bear, then back to the druid, and use it.

3. While the neutral item is on cooldown, you can do the following to crash the server: use items on an ally (not the bear), buy and sell an item, teleport, or summon the bear using Q. All of these actions will cause a crash. The easiest way is to buy and sell any item."

Credit: Dota 2

As a result, Lone Druid is banned in Dota 2 matchmaking since these steps were published.

This is not the first bug detected after patch 7.37 release allowing to hack the game server in Dota 2. Before that Denis "sikle" Lerman, Team Spirit analyst revealed another similar vulnerability with Enchantress-hero, which was explained through Aghanims Scepter item.

Remember how Edgar "9Class" Naltakian once described patch 7.37 meta and highlighted heroes suitable for MMR farming there?