Mutt: neomutt: bcc email header field is indirectly leaked by cryptographic info block

When using PGP encryption in Mutt or Neomutt, blind carbon copy (Bcc) recipients can be indirectly discovered by analyzing the cryptographic information attached to the encrypted message, defeating the purpose of keeping them secret.

Mutt and Neomutt fail to utilize PGP's --hidden-recipient mode during encryption, allowing attackers to infer Bcc recipient identities from the recipients information block in the encrypted message. This disclosure requires message interception but reveals information that should remain confidential.