Problem
Swarm Spawner mobs spawn with infinite duration potion effects. The Magic Siphon enchantment has a chance to transfer a positive potion effect from a slain mob to the player. This results in Swarm Spawner-based mob farms effectively granting massively overpowered infinitite duration buffs.

Suggestion
Add a (configurable) time limit to the buffs given to spawner spawned mobs. There's no practical reason why they need to be infinite duration.
Adding a similar option for boss mobs too, but with a default duration of several days would also prevent these from being abused too badly.

Versions
Minecraft 1.15.2
Apotheosis 1.15.2-3.3.8
Corail Tombstone 4.5.6

I am observing this still in a modpack I am playing, Explorico 1.3.

I originally posted about this here: #268

Versions as posted in the link above:
MC 1.16.2
Forge 1.16.4-35.1.4
Apotheosis 1.16.3-4.4.1
Tombstone 6.0.2

That should be resolved by that mod, probably by capping the duration of the effects that are transferred to the player. Potion effects on bosses are also infinite duration.