John 12:6 NLT

So not only did Judas betray Jesus, but he also stole money from the other disciples? Is this something John added in afterwards, or who knew that Judas was doing this? If the disciples knew before the crucifixion, don't you think they would have guessed at the last supper that Judas was the betrayer, if he was already known to them as a thief? Since Judas shortly thereafter committed suicide, it seems to me the statement of Judas being a thief is one that would have to be speculation on behalf of the author of John...