On the current rendition of the Scorn permanent apartments, the small space outside outside the apartment's main area (the space above the pay tile) can also be used to permanently store items before the apartment is payed for. This seems like it could be abusable for players in the first few levels before they can afford an apartment (its essentially a free apartment tile).
I tried removing the unique field from those tiles, but that did not appear to fix the issue.
It doesn't seem like this issue is easy to fix. I haven't investigated how player-unique maps are saved and loaded but I have a feeling that there's no way to fix the apartments that have already been created.
About the only way I can think to prevent new characters from abusing this is to tweak the apartment to have a common area that leads to the room, with the payment occuring outside the apartment map, thereby preventing the apartment from being abusable in that manner.
The problem seems to lie in how the map is saved -- the entire apartment is saved to the player's directory, so that first empty tile becomes usable as an apartment tile. Since this is probably necessary to make the rest of the apartment work right, the simplest solution is to redesign the map with the personal map behavior in mind.
When the fix is approached, we should ensure there aren't other maps with larger areas to abuse, too. I doubt this is constrained to only the Scorn apartments.
I can confirm, that this bug still exists. I've used the empty tile and the tile with the payment mat for storage that persisted over days. I've already read somewhere that the OLD apartment is kind of glitchy, but I still see it in the north of Scorn... perhaps we should copy ITS better layout to use for the new style apartments... and then rename that old apart map to something else (since I've also read that the area is still good for testing spells, or something like that).