Is it permissible to purchase an apartment through Murabaha financing, while paying a "hidden" (dark) sum of money to the seller?

The condition for Murabahah is that there should be no contractual link between the client who orders the purchase and the original seller, to ensure that the transaction does not transform into an interest-based loan. The contractual relationship between the client and the supplier must be absent. It is not permissible to finance a commodity for which the client has paid a deposit to its owner; rather, the contract between them must be canceled first. Accordingly, the amount the apartment owner is asking from you for its sale is not permissible, and your role is limited to guiding the bank to him so that it can purchase it for you.