It was originally a challange for Ghost in the Shellcode 2015 and was made by vector35. This is a rehost of that event so new people can experiment with gamehacking. This is summary from the original website

Welcome to Pwnie Island!

Pwn Adventure 3: Pwnie Island is a limited-release, first-person, true open-world MMORPG set on a beautiful island where anything could happen. That's because this game is intentionally vulnerable to all kinds of silly hacks! Flying, endless cash, and more are all one client change or network proxy away. Are you ready for the mayhem?!

Features

Like most modern MMORPGs, Pwn Adventure 3 features plenty of...

Quests

A large, open world isn't useful unless it's filled with quests. So, just in case the bears and hacking challenges don't keep you busy, we've packed in more quests than ever before. You'll be doing quests until the cows come home!

Bosses

If world bosses with epic and legendary loot is your thing, we have a game for you! But, beware - some bosses may need more than your buddies and some upgraded gear to overcome...

Player vs Player

Do you find first-person, player-eat-player action exhilerating? We've got you covered with a toggleable PvP mode available all over the island. But, don't forget - we encourage cheating. Make sure your aimbot is as good as your opponent's!

There's also a large island to explore, epic loot, hidden areas, achievements, pirates, and more!

Rules

Do not attack the gameservers directly or otherwise try anything malicious which might cause other people's exerience to be degregated.
Otherwise this is a game hacking challange, so you are free to modify game files and manipulate network traffic as you wish.
There are writeups online, though you only fool yourself by using them
GLHF!