فإن اطلع المشتري على خيانة في المرابحة فهو بالخيار عند أبي حنيفة
Translation: If the buyer discovers dishonesty in murabahah, Abu Hanifah gives the buyer an option.
The buyer agreed on the understanding that the original price and the disclosed profit were accurate. Misstatement defeats an important expected feature of that bargain.
The option does not itself mean an automatic reduction of the price; the buyer can maintain or reverse the transaction as the next wording explains.