You need to contact your building services. You clearly have leaks in that wall. Smell won't go through two panels of sealed drywall and whatever insulation should be in that wall as well.

I guess you could say your walls are "Toilet-Paper" thin??

*quietly sits here, waiting for the first person to make the "shitty situation" pun*

You could open a yankee candle in your apartment and fight the smell with lots and lots of candles. Just hope your thin walls aren't also fire hazards!!

That means they probably smell you too so Fml all around ig. ☺

This sounds like it'll turn into the worlds first poop war......what a sad sad time it is

Build a better wall! Make OP's bathroom great again!

Ask your neighbors nicely to make sure they use the toilet for pooping. Pooping in the room that coincidentally has the toilet is not "close enough."

It's probably that the vent fan ducting in both of your apartments is connected together, so it's easier for their poopy air to go into your place than out the ductwork. A piece of cardboard over your vent fan, removed when you need to use it and replaced afterward, will do the trick. Or you can leave your vent fan on all the time, which is neither energy efficient or good nor good for the fan.

if you can smell their poop, then they too can smell yours. perhaps you should start eating more mexican food.