5.4.7: Entirely changed gamerule. Instead of applying Fragility at max level, all hostile mobs will instead constantly target the nearest player.
11.1.5: Revised functionality as of the (undocumented) change in v11. Entities are now pinged every 200th world tick instead of only when an entity spawns.
11.1.8: Improved performance for Universal Hatred and Insanity Mode (Universal Hatred, instead of looping all entities on effect application, then looping through all entities again to target, will instead use a global boolean flag alongside the world tick checker. The same has also been added to Insanity Mode which "pings" all hostile mobs immediately on player join)