Decrypted S/MIME parts, when included in HTML crafted for an attack, can leak plaintext when included in a a HTML reply/forward. This vulnerability affects Thunderbird < 52.9.
http://www.securityfocus.com/bid/104613
https://access.redhat.com/errata/RHSA-2018:2251
https://access.redhat.com/errata/RHSA-2018:2252
https://bugzilla.mozilla.org/show_bug.cgi?id=1419417
https://lists.debian.org/debian-lts-announce/2018/07/msg00013.html
https://security.gentoo.org/glsa/201811-13
https://usn.ubuntu.com/3714-1/
Source: MITRE
Published: 2018-10-18
Updated: 2019-10-03
Type: CWE-200
Base Score: 4.3
Vector: AV:N/AC:M/Au:N/C:P/I:N/A:N
Impact Score: 2.9
Exploitability Score: 8.6
Severity: MEDIUM
Base Score: 6.5
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Impact Score: 3.6
Exploitability Score: 2.8
Severity: MEDIUM