Spiders with status effects will pack spawn, so you will often see multiple spiders with the same potion effect in the same area.
Further, this is not the case for spider spawners, as only one of the 1-4 spiders will have the effect.
Steps to reproduce
- Play on a world on hard difficulty and a high regional difficulty (~6.00 or so)
- Make it night time, but don't use /time set night or similar, because it will mess with the local difficulty. You can use /time add 1000 repeatedly though.
- Wait for spiders to spawn
- Find spiders with status effects
- Notice that there are usually 2-4 in a small area all with the same effect, instead of just one
This is in an area where the local difficulty is ridiculously high, you must be on hard difficulty to see spiders with status effects, and even then it is a rare occurrence.
Possibly intended, but was an unannounced change.