LilleCarl reported a bug possibility that you can buy items from the last multivendor you were at IF:
You are near at an NPC with vendor flags
You have not clicked on any normal vendor in between
You send buy item packets while being near the vendor NPC (any vendor)
(Note that all security and faction checks and costs are still the same for the item, this is only a possible exploit to buy the items elsewhere than at the vendor)
Its not really a bug I would consider major though .. Unlikely anyone is going to go through all that trouble to buy items they could buy normally at the vendor anyways.
So Ill fix it if I get around to it : |