UnioAntiCrash is a Spigot plugin to solve 1.8 Turkish client crash. It used by thousands of servers and still going.
This plugin prevents players to use a specific character that crashes clients older than 1.8.7 and using Turkish language. It's solved by Mojang for newer clients but there are people still uses older clients. If you don't allow your players to join with 1.8 you don't need this plugin.
More info: [Bug MC-80875] – Specific unicode character pair crashes tr_TR clients
Yes, it is compatible with both.
It works from 1.7 to 1.16.
Try to send this text to chat with a Turkish 1.8 Minecraft client: "asd454614564137564645654iİsd32rsdcfvdİfsdcsd45r6dsf57sdf54687684687778444444444cfsdf32454566234fSDB;"
1- Drag the UnioAntiCrash.jar to plugins folder.
2- Edit config.yml if you want to change messages.
3- If you want extra protection drag this plugin both Bungee and Bukkit.
4- Restart your server.