Accusation that someone is cheating, benefiting by performing sexual favors for the right people. The phrase originates from a MUD (Multi-User Dungeon, a text-based MMO) by the name of Materia Magica (originally Moongate), primarily run by a guy going by "Vassago". The phrase accused a player of benefiting by sleeping with the game's main administrator.
You seem to be getting pretty lucky lately. Looks like someone has been sleeping with Vassago.