Exploit

On ROBLOX, an exploit (informally referred to as a hack) consists of using a bug, glitch, or vulnerability in ROBLOX's software to oftentimes maliciously manipulate the game in a way that is not intended by its designer. ROBLOX considers exploiting as cheating and is not allowed on its service. People who use exploits in an unfair manner are known as "exploiters". Exploits can be used to advertise games, gain advantages in a game, attack a player or group, or to show that exploiting is possible.

Rumors have formed and propagated on ROBLOX concerning exploits and the many exploiters that use them. Many theories of questionable value have been proposed about the actions and identities of users such as Dignity and 1x1x1x1. Most of these rumors generated a cult-like following that glorifies such users.

History
During the history of ROBLOX, many exploits were found, disseminated, and abused by ROBLOX users. Most of those were, over the course of development, fixed by the ROBLOX developers.

There is no solution to completely eliminate exploits on ROBLOX. However, many advances towards reducing exploiting have been attempted.

Cheat Engine
Cheat Engine, a debugger and exploiting tool for Windows created by Eric Heijnen, was commonly used to take advantage of various vulnerabilities within ROBLOX. Its numerous features have given life to many ROBLOX exploits. These include exploits such as speed hacking, which causes the ROBLOX client to run faster, memory editing, which changes game values by finding and editing values in ROBLOX's memory, and dynamic-link library injection, which manipulates coding by injecting a DLL file into ROBLOX's software. Most of these exploits have been patched by the ROBLOX developers. ROBLOX is currently attempting to patch cheat engine but people have ways of getting past the MemCheck security update.

Lua bytecode
When Lua runs programs, a virtual machine compiles code to Lua bytecode before it is interpreted. This process is irreversible, and thus was frequently used forCode Obfuscation.

Lua bytecode does not have the same structure as Lua and allows, by unconventional means, manipulation of the stack and other things that are not possible in normal Lua programming. It is possible, though difficult, to write Lua assembly code manually and to assemble it into Lua bytecode. The ROBLOX process can load Lua code and Lua bytecode through use of its  function.

It has been proposed on the Lua mailing list that direct stack manipulation could be used to access the environment of other functions during their execution and, therefore, to steal values from these functions (including C functions that Lua has access to), something which is not possible in pure Lua.

The ROBLOX user NecroBumpist proved the idea to be true and possible. Using Lua bytecode, he created a function that allowed a script to steal values from other functions, including C functions. This made it possible to steal values from ROBLOX's API's, but months passed until someone found a way to use this bug to modify the global environment and to become capable to make the core scripts and the join script execute any Lua code in a game server.

This resulted in the removal of bytecode and the ability to use it with the loadstring function. Despite common belief, this exploit was unrelated to a DLL exploit in the same time period. The removal of bytecode had no other side effect than rendering code obfuscation impossible without other means.