The only knock off Hot Toys issues I’ve had, was buying used from comic shops and someone got a third party killmonger sculpt past me, and I didn’t really realize it until I got back to the hotel and opened him.
Then not really knock off, but at a toy convention, I traded for a “as is” mechanic Stark a few years back. And after the fact I realized that while an official head sculpt, it wasn’t the proper mechanic one, but a bleeding stark from another Hot Toy.
So I would just recommend watching a review/unboxing video or two of the figure you plan to get, and make sure it matches up with what you are getting pretty exactly.
I usually check stickers with Figma, they have a lot of knock offs. Hot Toys has a occasional Disney sticker, but aside from being mindful of third party figures, or maybe a recast sculpt from what I read here, I’ve never had a full “knockoff” issue.
Always stay as smart and vigilant as you can.
Ask the seller about the sticker, could be a security tag, or sale indication , or maybe even a new/used indicator. Always best to ask , and get in writing when possible.
The Killmonger I knew was open, but the shop told me it was new and just opened for display, which is how I found him.
So if it’s a open box figure, you can maybe ask for more pictures of the contents and can double check a unboxing
Best of luck , sorry for the ramble lol