Hi! I've seen some players crashing my server, by hitting in the air. It will lag the server extremely much, and will crash it after 1 minute. Is this a client? How can I prevent it?
Sounds more like a potential plugin exploit...if this was a unanimous bug across Spigot, no way it wouldn't be everywhere. Plugins? Evidence it is directly caused by this activity?
Evidence is, that I can ipban the player and then he joins with VPN does the exact same thing while saying "Haha crashing the server".
Plugins list, may be logs (when a player "crash" your server). Put the crash log please. We can't help you without any information.
It could potentially be a plugin fault especially if it's doing server heavy things on PlayerInteraction. Mind doing a Pastebin of your log containing the user when they attempt to crash it and a list of your plugins being currently used. Allows us to try get to the issue
I've seen a plugin with a region protection (...) feature help crash your server, because it registered events to process them first, so plugins protecting against spamming interaction would receive already cancelled events and ignored them, and the plugin with the region feature sent a an unthrottled message with each interaction, so the amount of messages sent back crashed the server. You can do many things including switching to whitelist , but the most promising path to finding the cause is to check plugins and crash logs (and server logs and plugin logs, where plugins log things like security/safety violations).