Is it permissible to buy goods that have large promotional offers, such as "buy two items and get the third free," without knowing the seller's intention behind this discount?

The aforementioned issues fall under the promotional offers and gifts that merchants provide for marketing purposes, and there is no harm in benefiting from them. This is because the buyer receives a price reduction or free gifts, and it is permissible for the owner of the merchandise to reduce its price or give a gift with it to the buyer.