Yes, a laser can damage a digital camera sensor, especially if it is pointed directly into the lens. Stronger lasers are known to cause permanent sensor damage, sometimes leaving visible burn lines. Lower-power presentation laser pointers are much weaker and may be less likely to cause harm, but there is still some risk, so it’s not something to rely on as safe.

Possible damage isn’t limited to the sensor itself; the color filter array over the sensor could also potentially be affected. For light painting, it’s safer to avoid aiming the laser directly at the lens and use an LED or incandescent light source instead.

Also protect your eyes: don’t look through an optical viewfinder when working with lasers. If you must test anything, use live view and keep the beam away from the lens.