It is possible to execute JavaScript in the parsed RSS feed when RSS feed is viewed as a website, e.g. via "View -> Feed article -> Website" or in the standard format of "View -> Feed article -> default format". This vulnerability affects Thunderbird < 52.5.2.
http://www.securityfocus.com/bid/102258
http://www.securitytracker.com/id/1040123
https://access.redhat.com/errata/RHSA-2018:0061
https://bugzilla.mozilla.org/show_bug.cgi?id=1411716
https://lists.debian.org/debian-lts-announce/2017/12/msg00026.html
Source: MITRE
Published: 2018-06-11
Updated: 2018-08-07
Type: CWE-74
Base Score: 6.8
Vector: AV:N/AC:M/Au:N/C:P/I:P/A:P
Impact Score: 6.4
Exploitability Score: 8.6
Severity: MEDIUM
Base Score: 8.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 2.8
Severity: HIGH