Strange undeletable wireframe cube

Hello there.

Does anyone know what this wireframe box is? And more importantly, how to get rid of it?

I’ve had a few times now that while I’m working on a model, I must have mispressed a key or something, because at some point I can suddenly get some wireframe box that is unselectable in the edit mode, dissapears when i turn off Overlays as a whole, yet remains when I turn off each overlay option individually. Even if I select specifically the parts of the model and seperate it, it carries over a duplicate of that wireframe cube. I have no idea what it is and how to get rid of it.

Hi, we need to see the file to be able to help. is there a modifier in this object?

Here it is. Thanks.
And no, there’s no modifiers used.
Another peculiar thing I noticed is that when I apply location of the object, that cube moves.
Hopefully it all makes sense eventually.

weird wirecube.blend (1.7 MB)

This is the objects “texture space”. Not sure what exactly it does, myself.

To turn it off:
Properties editor → Object tab → Viewport Display panel → uncheck Texture Space.