You aren't the only one to have noticed this. It happens to about 6% of the customers starting September 14 2019.
Let me just start by saying you are not now, nor will you be double charged for anything. Furthermore we pride ourselves in providing great customer service and work hard to build your trust. Should anything happen, rest assured we will be sure to make it right for you.
Anyway, on to the explanation https://stripe.com/guides/strong-customer-authentication
Basically new rules for some customers make it harder to make a purchase. Without getting to technical what happens is a charge shows up on our side that appears as (UNCAPTURED) and on your side it shows up as "PENDING". No money has exchanged hands at this point. Once the purchase is complete a charge is made and the pending charge falls off.
I don't know if the system for the 3rd party (not curvage) is still a bit weird. For some the pending charge disappears right away, for others it takes a bit longer to drop off. However, it does go away and there is no double charge.
I hope this helps.