Toilet Bowl Leak

I own an apartment in a coop building. A few weeks ago, my neighbor directly under me notified the building that there was circular water damage on her bathroom ceiling right beneath my toilet bowl. The building called in a plumber, who indicated that my toilet was the wrong size, and the size mismatch is causing the leak, so it needs to be replaced.

There are a few things that feel fishy here:

- The bathroom and toilet were renovated a decade ago, and this is the first time this problem is happening. I bought the apartment a year ago, and while I have had a few clogs (no overflows), I don't see what has changed.
- The super is saying that there is now water damage all the way down to the third floor (I'm on 8). But how can my toilet bowl affect an apartment on the third floor? It seems that the water would drip down to the ceiling directly beneath me, but how could it get all the way to the third floor?

I think they are yanking yer chain. I believe all floor mount toilets have the same outlet to mate to a floor flange. The wax ring may have lost its seal and caused the leak or the pipe could be old an rotted. Who is responsible to maintain the drainage piping, you or the building owner. Tell the plumber you want the old toilet to verify its the wrong size. I would guess the building super and the trades he uses to work for him have a little deal going.