Game developers are not oblivious. Popular Copter.io clones and the original servers implement several countermeasures:
Scripts from untrusted GitHub repositories can contain malicious code designed to steal browser data. copter io hacks github
Most GitHub repositories for .io games focus on a few core "quality of life" or competitive advantages: Automatically targets the nearest enemy or crate. Speed Hacks: Modifications to movement velocity. Rapid Fire: Removes or reduces the cooldown between shots. Copter