I just proposed that as a crackpot theory. At a bare minimum we know for a fact a leak exists, since the plot is literally impossible without one. And sure, heroes in this series have brought this up a number of times. And of course, the most likely scenario is that there actually is a specific traitor. But given recent developments I do think sheer incompetence would actually explain what has been happening. A traitor is without a doubt the most likely scenario but the idea that heroes are so inept that they just keep leaking this information somehow (via someone gossiping, backdoor to their communications, talking about this type of thing within earshot of a villain) is at least plausible. Most of the stuff the heroes plan ends up failing so the same applying to their security makes sense.