Minecraft Server Item Grief?

It's about a grief that someone tried on my Minecraft server. This person has given an item a tag: "http://www.wurstclient.net: [[], [], [], [], []]" and so on. I couldn't see everything because the string was too long. The thing is, two people took this item, and then got kicked, and got kicked every time they join. Because of these items you could no longer access the server. In the console there was also an extremely long exception. You had to clear the cache for the server, so clear inventory, then it worked again.

Can someone tell me where this person who created the item got this day or the command to create this item?

This is a crash item that the person got via the Wurst Hack Client.

OK thanks!