Support. It's shocking how something this simple, but also very exploitable hasn't been fixed yet.

+1 - It is so annoying in multiple situations to have to wait for a gm to get on and do something only they can do. Also, in wars, having only advisors or gm set the allowance has limited who can place traps consistently. 

The most sickening thing about this saga is how the guild thief publicly boasts about purchasing better gear using their ill-gotten gains in the Sailing Discord. What's worse is that certain items such as black crystal cannonballs might have little monetary value to the thief, but take guilds weeks or even months to build back up.

While I understand the thief might be salty about the way they were treated by a previous guild in the past, it's unfair to take this out on other guilds. Furthermore, their actions hurt smaller guilds more than it does larger guilds. Not only are smaller guilds less likely to have a stringent recruitment process involving multiple layers of Discord interviews and referrals, it also takes them significantly more time to accumulate the materials they lost because of the limited man-hours they have to sea monster hunt, do guild bosses, or even collect guild login rewards.

As many others have pointed out above, the ramifications of this exploit are widespread and damaging for new and returning players alike. Guild leaders would be compelled to operate on an "invite-only" basis and decline requests from players whose quality can't be verified by those inside. At the end of the day, community is one of the most important aspects of the game that brings me back—even if I fail my PEN BS tap or fail to get the Elten piece—and I'd hate to see the community become suspecting of one another just because of a couple of bad apples.

As for practical solutions PA can implement, I second the solution posted by Pirate Beowolf to allow Guild Leaders to set permissions for who can withdraw materials from guild storage. That way, sea monster hunting guilds can allow valuable materials (perhaps with the exception of monsterbane cannons and cannonballs) to be withdrawn by officers, while node warring guilds can allow new recruits to take what they need from guild storage. Guilds shouldn't have to restort to tedious workarounds of storing mats in guild galleys or Officers' alts.

The Staff tell us to be more careful, well this is my method.
Please tell me if you are even close to take this method and if so how can we protect against theft?

Web google forum. DIscord ID and Family ID and questions regards game play and former guilds.
I search BDO Discord, Sailing Discord for both, and reach out to former guilds if listed ( know most or the know of me lol )

I ten move to a discord text interview and if I feel they are not full of caca well I invite them.

And yet they got in 3x since 2018