The bug can be used in 3 of the 4 maps available in WvWvW so you already know its not the one with the Castle.
SUPPLY CAMP (the one South only)
The roof’s building behind the supply is reachable once the camp has reached 100/100. then you can walk on your right and you will see a chimney kind of. You can set up an arrow thrower (sorry for the translation) by searching for a spot half on the roof half on the chimney.
Once you managed that, stack up on the construction and finish to supply it. Once the weapon is built all the people stacked on it go through the wall of the chimney and can’t get out
Since the chimney is right next to the guild master you have to kill in order to reclaim the camp, people with bad intentions might want to use this bug. You would just need one person blocked in the building and no matter how many pple try to reclaim the camp it would be impossible.
Hope I was clear enough!
Btw it looks like a chimney but it’s just a small room with not even a bed in it
we felt like being in jail!!!