2037358 - BCC recipients are revealed when sending signed emails

Status: RESOLVED FIXED

(MailNews Core :: Security: OpenPGP, defect)

Description

[Simon B]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:150.0) Gecko/20100101 Firefox/150.0

Steps to reproduce:

Send a pgp signed email and put recipients in the BCC field.

Actual results:

In the source of the email, both the recipient and the BCC recipients can see the complete header, including all recipients and BCC recipients.

From the perspective of the recipient and the BCC recipient, it looks like this:

...
This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
--------------rz4dz1YID2M8tbJi2AXsqELN
Content-Type: multipart/mixed; boundary="------------XLomQTo4ISWeDmiZo1LSHr2Z";
protected-headers="v1"; hp="clear"
Message-ID: <[e-mail]>
Date: Wed, 6 May 2026 10:39:32 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
To: <removed_recipient>
Bcc: <removed_bcc1>, <removed_bcc2>
From: <removed_sender>
Subject: test
Autocrypt: addr=<removed_server>; keydata=
...

Expected results:

With signed emails, it is not necessary for the email addresses of BCC recipients to be visible. Therefore, these addresses should not appear in the source of the mail.

Otherwise, a warning should appear, as it does for encrypted emails with BCC recipients.

Comment 1

[Magnus Melin [:mkmelin]]

I think from bug 1959096

Comment 2

[Magnus Melin [:mkmelin]]

Attachment: Bug 2037358 - Don't include BCC recipients in signed headers. r=kaie

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/comm-central/rev/f07c8aae42fb
Don't include BCC recipients in signed headers. r=kaie