Developing or using exploits violates Roblox's ToS. This answer is for educational discussion of software design patterns only.
KRNL is a widely recognized Roblox script executor. Developed by a team of dedicated contributors (most notably Ice Bear), it allows users to run scripts within the Roblox engine. While Roblox has a built-in security system designed to prevent code injection, executors like KRNL bypass these restrictions to allow for custom Lua code execution. KRNL Beta Exploit
Most exploits crash because they try to reinject or re-scan the Lua environment every time a script runs. ACC solves the two biggest issues in beta software: lag spikes and signature scanning . Developing or using exploits violates Roblox's ToS