Whenever a mob spawner spawns a mob it can do it inside a solid block.

I found the issue when I was making a blaze farm and I was using blocks to prevent spawning. I was surprised when I saw blaze spawning INSIDE the blocks. I first spotted the issue in 14w27b, but assumed someone had already reported it. When I saw this issue had not been fixed in 14w28a, I realised that I needed to report it.

Thanks a bunch!!