Every platform sells fake Fragrance bottles sometimes... Flipkart, Amazon Myntra, big basket everyone. Platform is not always responsible. Sellers are. This is a great supply chain authentication and management issue. Especially for expensive international brands. But it's not too difficult to identify fake ones if have basic knowledge about that particular perfume.
TLDR • only buy from Reputated Flipkart Assured and Amazon Fulfilled sellers. Check bottle and box labels. • Check Fragrance notes from site fragrantica. Check if your fragrance has similar notes.
• Check bottle label and box design , label, printing for etc. for poor quality or imperfections.
I think Myntra sells fake perfumes. Read many many reviews.