This happened to me that year as well and at a Marriott property.

I was in traveling in Western Europe and did not have any issues for most of my trip. I check into a new hotel in a good country, one that you don't expect fraud in. That evening, someone must have taken my membership number and booked two rooms in another Marriott hotel in the same country, but in a different city (2 hrs away). The only way I found out was when I was checking my Bonvoy app the next day. I saw two reservations and thought it was a glitch. I did not get any email for the reservations either. It was several thousand dollars for the rooms. I called the hotel directly and asked about the reservation and they wanted to charge me a cancellation fee! I explained it made no sense for me to book the rooms when I was staying in another city. The front desk person was not helpful but when I mentioned I was going to call headquarters they reluctantly cancelled and waived the fee. I ended up calling the Marriott Titanium hotline and they launched an investigation after I explained the situation. They couldn't really answer how 2 resverations wouldn't send an email notification and made me set up extra security. I've never had any issues with my account. for the many years I've been a member. After a few months they got back to me and said their investigation didn't find hotel staff were involved. I always thought it was a bunch of BS and now this video makes me think Marriott is aware how fraud is easily done by using a membership number.

I highly suspect hotel front desk passed my membership number and they booked in the extra rooms via the other hotel's reservation system. Probably thinking they'd charge me and let my credit card take the hit and fraud protection cover the expense (I'd be unaware because I'd have charges for my primary stay). I found out the second hotel is known for criminal activity in that particular country. This video totally makes me think it's an inside job because how else would someone know to use a membership number that has payment details saved.