This is a simple plugin that prevents most god mode bugs and exploits from functioning. Currently, the server allows the client to determine when to decrease noDamageTicks (The small interval between hits where you're invincible). This plugin puts the server in control of noDamageTicks, so if the client stops decreasing noDamageTicks the server will do it for them, ensuring players can't elongate their short invincibility between hits.
With this fix, the current behavior is that players who 'lag out' or crash, in addition to people who intentionally exploit, will receive damage at the same rate as a non-lagging/non-exploiting player, whereas without it, these players will be invincible until they stop lagging/close their client (if they crashed)/stopped exploiting.
No configuration is required, once installed it functions automatically.
