According to various reports, players are instantly levelling up under mysterious circumstances in Season 5.
Weisshuf was killing Aether Lords when suddenly, the whole party got enough Experience to go from Level 70 to 100. You can watch the Twitch clip below.
A similar thing happened to Neamins who leveled from 29 to 63 by doing the Stronghold boss.
We do not know what’s causing the bug, and recommend anyone to not abuse this as it may result in account penalties.