Updated from snapshot 18W32A to 18W33A and there are mobs everywhere. Even in lit areas (light level 8+)
Creeper spawned in light level 12
Slime chunks have increased
Mobs are spawning ontop of blocks with torches
Environment
Operating System: Windows 10
Java Version: build 1.8.0_181-b13
Minecraft Launcher (not Windows 10)
Bootstrap: 1636
Launcher: 2.1.1351
UI: 26
I just reported the same issue (136086)