Roundcube before 1.3.7 mishandles GnuPG MDC integrity-protection warnings, which makes it easier for attackers to obtain sensitive information, a related issue to CVE-2017-17688. This is associated with plugins/enigma/lib/enigma_driver_gnupg.php.
https://roundcube.net/news/2018/07/27/update-1.3.7-released
https://github.com/roundcube/roundcubemail/releases/tag/1.3.7