As per international finance practices, there will be a price difference between buying and selling a financial product. To prevent guaranteed arbitrage and reflect the holding cost of a financial product, the ask price is usually higher than the bid price.
Due to the short-sellable trading feature of CFDs, the ask price indicates a price at which the investor is willing to purchase and hold an object that they expect its price to go up. On the contrary, the bid price is a price at which the investor is willing to purchase an object that they expect its price to drop.