How to best deal with that?
I would say we have a few options.
- Leave a comment on the accepted answer with the updated information and ask the author to add the info.
- Edit the answer with the new info (for example, I've been trying to do this on a previous answer I supplied)
- Add a new answer with the updated information.
- Ask a new question which has a reference to the old question. The new question could say something like "how do the results of paper X change the answers to question Y here on Crypto.SE". Then either edit question Y to include a link to the new question or add a comment on question Y to the new question.