I had my items stolen and sold off the same way like OP posted.
-never shared password/strong and secure password

I log out to sleep and when i got back from work i had my 2 rarest pieces missing and my gils,
people reported the same suspicious behavior where both were being sold for 200k each in sandoria with my character and had my stuff missing ever since, granted it wasn't 20 million loss but to a new player like myself it was worth everything.

not sure whos is the culprit, but i hope they get caught.

My account got compromised, not long after Lithorn got jailed. I'm unable to reach out to Nas to confirm anything. Seems he has decided its better to jail away to prevent some loss. Thing is it was a bit too late. I don't know how many months I had been comprimised, I do know some stuff went missing. Now I no longer can play Lithorn, even after changing all my passwords. The timeline has to be between Jul18-2018-Jul20-2019 As thats the times I posted on the forums and remember playing.

When I say some stuff went missing, I lost my Hairpin, Boots and my signed Iridal from Sab. They bought a Royal cloak for some reason which is a waste of gil. The Mp tick is the same on the vermy.

I still had a lot of my stuff in my MH, so I don't know if I was comprimised for very long. When I had came back wantin to play I noticed my password was wrong, and that Lithorn was marked as Online. This is when I used the forums to boot the account and changed the passwords. Around Jul 20th 2019 is when I noticed. I played for a few days after, trying to figure out what happened or what I was missing. I ended up giving up and went on to playing Wow again.

As for gil, It had been so long that I didn't remember how much I had. When I looked at lithorn I think he had around 250k and that was mostly still there, or maybe it was 50k. I wasn't worried as I mostly just mine Oore for gil and can make that back easily. I don't know what all I am missing in full but it still seems like its all there. I think I got lucky and caught on before too much damage was done, and am hoping Nas will revisit my jailing.

I thought everything was fine after I changed my password, but to come back to being jailed. Either they got my password again or they did something wrong when they did have it. If the forums are leaking then it wont matter what I change it to. Thing is this website isn't the only one that has had leaked information. Firefox has reported several sites, including mod forums like nexus.

I don't use cheats, I did use updated map dats which Nabu told me to undo and I did. ( I still think its dumb that you can google these maps on ffxiatlas or allakazam, why they can't be used as a map overhaul I dunno. They are not like the map addon that gives you free maps, they do have updated information that everyone can access online, but I don't make the rules.) I think the only wild addon I ever tried was the ExpWatch but it never worked so I tossed it. I don't sell or buy gil, nor would I give anyone my account. Lithorn is, was, mine. I've spent many years off and on, though not as long as some, playing with him.