plz tell me how, im using imageapp on manjaro.

And you say you were playing as Athens, right? If the territory gained from the building you captured ends up touching your own territory, then it’s expected that it won’t decay (even without garrison). But if the building remained isolated (not connected to your territory) and it was ungarrisoned, then that would indeed be a bug. Do you have the replay? It would be good if you could share it so we can check what happened. If you don’t know where to find it, you can go to the replays window, identify the match, and at the bottom you’ll see a text box showing the exact file path.

this is so weird, we need you to share the replay  

ok, sure. i captured buildings, outside my teritory root, the buildings did not decayed, i was able to use them, outside my teritory root, ungarrisoned.  i checked several times, the buildings didnt started to loose ownership - the things did not decayed. my gamebud recaptured, and, shazamshazam, abracadabra, hocus pocus, under his ownership, buildings started to decay.

I don't understand very well your first message, @dinuruian. What is actually the exploit? Could you please rephrase?