When a transaction is received by Edge Wallet, this is almost immediately shown in the transactions history of the wallet, marked as Pending (in red) and the balance is updated.

This is true also for the so called RBF transactions.

In the italian version of the app, "Pending" is "In sospeso"

What is a Replace-by-fee (RBF) transaction?

Replace-by-fee is a Bitcoin node policy. There are many variant of this policy, however, to simplify, we can say that a wallet that use RBF allows an unconfirmed transaction to be replaced with another transaction that use the same input as the previous but a higher mining fee.

Let's say a user send a transaction to us, using a wallet that support RBF: he could send it using a very low fee, for example 2 sats/byte but he may later realize that the network is congested, so he could replace that transaction with a new one with the same amount but with a higher fee, for example 15 sats/byte. This way the transaction will be confirmed faster.

An example of RBF transaction, 2 sats/byte

This policy could be use in theory to create a scam attack:

an attacker could send an amount in bitcoins using RBF and ask the receiver to send goods/other currencies in exchange.

After the exchange, the attacker could potentially "cancel" the unconfirmed transaction by diverting the same inputs to a transaction that pays an address he owns.

After the confirmation, our wallet would remain without those funds and we would also have sent the goods/other currencies to the scammer.

This is a very uncommon scenario however here you have two useful steps you can follow, if you want to be safe:

  1. Never send goods/other currencies if a transaction has not yet been confirmed.
    When you receive a new transaction in Edge, you see that is marked as "Pending". That means it has not yet been confirmed by the blockchain and you can monitor the confirmations by clicking on View advance transaction data --> Show in Block Explorer.
    Here you will be able to check if your transaction is still in the mempool or has been confirmed and how many confirmations it has.
  2. Use a type of transaction called CPFP (Child Pays For Parent), fully supported by Edge Wallet, so you should be able to confirm the RBF transaction before the scammer.