Red blocks in photoshop cc 2015

Just started noticing these today when I'm masking. What's going on?

Weird, if this was a computer game, it could be either video driver issues or too overclocked. Still could be driver issues though

When you say masking, are you in quick edit mode (and instead of a red overlay over the whole image, there's just a few pixels)? I've seen that happen before due to low memory allocation. If this just started now, you could try resetting your prefs. Or you may need to adjust memory settings.

Check your brush. Make sure it's a normal round brush.

The pattern you show is what you would get if you did "quick mask" with a strange square brush that had some combination of jittering, scattering, shape dynamics turned on.

http://damiensymonds.b​logspot.com.au …ther-weird-behaviour.html