Until now in Pirates of the Burning Sea, some clever folks have been able to cause a totally peaceful port to instantly become scheduled for a port battle, by saving up their contention turn-ins en masse and across characters, and handing them in all at once. Over at the official PotBS site, Isildur has drawn attention to the issue and said that changes are coming to prevent this from occurring in the future.
You couldn't really call this tactic an exploit -- it's more just a smart use of the mechanics available in the game -- but it's obviously not how Flying Lab Software intended for the whole process to go down. The plan was to make the contention process a bit more steady so that the home nation could have a chance to defend and bring the unrest back down again, and possibly save a full-scale port battle from occurring, while also giving the traders a bigger role in defending their business interests. The first steps to prevent the current insta-port-battles should be introduced with build 1.2.