Like, no doubt, many of the other folks on here who have 30+ years in the IT biz, I've done my time working in security-focused roles...
There's this thing called "responsible disclosure"
You find a vulnerability...
You probe it enough to prove it CAN be exploited and maybe even in the process develop a proof of concept method...
Now at this point you're just like every other geek in the known universe, we all poke at stuff to see where it can break and what kind of pretty pieces fall off when it does.
Unless you're a black hat or in this case a game cheat, what you don't do at this point is go off and start exploiting it for yourself and/or your buddies. (Yes, I know there are real-world "grey areas" like so-called hacktivism or other ways of "sticking it to the man" or targets that for one reason or another "had it coming" - they don't apply in the context of game cheating so I'm specifically not addressing those here. There is no "greater good" in cheating a game.)
You document it for the folks responsible for the faulty code. In this context that means a bug report to FD, made via a ticket, not a publicly readable forum post. Then you give them a reasonable time to do something about it.
If they do nothing you disseminate the info to the wider security community - this is still not "going public" with it and you're not releasing it "into the wild". You're simply recruiting fellow-advocates who may have a more effective communication channel to the folks who can fix it than you do. Here this would be talking to players with a presumably decent channel to FD, people who have stepped up as ambassadors, leaders of community groups, even forum moderators since they may be presumed to have some proper way of getting FD community management to take a look.
Only in the last resort do you go public.
AND YOU STILL DON'T USE IT YOURSELF OR ENCOURAGE ANYONE ELSE TO - In fact, if you become aware of anyone doing so you report them as loudly as you can.
There has been no evidence that 13th Legion followed this responsible path. So no. Nothing heroic there at all.