This document describes techniques and apparatuses directed at detecting and preventing light-based injection attacks. In aspects, a computing device includes executable instructions of an input manager, an audio sensor having subtracting circuitry, and a light sensor. One or more processors executing instructions of the input manager is configured to receive and analyze signals generated by the audio sensor, the light sensor, and the subtracting circuit. Upon analysis, the input manager can detect and prevent light-based injection attacks.