First link demonstrates reading from uncleared buffered to capture screen contents - and is from Windows XP era. Second one is about running a bitcoin miner on

First link demonstrates reading from uncleared buffered to capture screen contents - and is from Windows XP era. Second one is about running a bitcoin miner on the GPU, hypothetical memory breaches, and GPU DoS. You can stall the graphics pipeline without shaders, run a miner on CPU, and I'm going to need a demonstration of a usefull GPU memory breach with WebGL. On top of that any such breach is likely driver dependent and will only work on some specific driver/HW combination - that's such a low attack surface I doubt anyone will bother developing exploits targeting that. I didn't bother going through third because I wasted enough time on first and second, I don't see how anything here suggest you need to sandbox shaders.