docs(coinjoins): add new fault for bip78 in a social usecase

Author: johnsBeharry

bip78-adapted.md

@@ -78,4 +78,6 @@ sequenceDiagram
 > *another possibiility is for the receiver to pre-fill their input(s) in the first stage, and save on the last interaction, but that's not how bip 78 is specified, there the initiator is the sender and you don't wan to reveal UTXOs to fake senders*
 > -- @nothingmuch
 
-This may be so in an online shopping scenario when you are interacting with a merchant, but i think this would be different for a more social use case.
+This may be so in an online shopping scenario when you are interacting with a merchant, but i think this would be different for a more social use case.
+
+Not only does this expose the receivers inputs to a potentially malicous sender — but it may be possible that the sender receives a payment if they broadcast the transaction.