kf5-messagelib vulnerabilities

Damian Poddebniak, Christian Dresen, Jens Müller, Fabian Ising,
Sebastian Schinzel, Simon Friedberger, Juraj Somorovsky, and Jörg
Schwenk discovered that PIM Messagelib could be made to leak the plaintext
of S/MIME encrypted emails when retrieving external content in emails.
Under certain configurations, if a user were tricked into opening a
specially crafted email using an application linked against PIM Messagelib,
an attacker could possibly use this issue to obtain the plaintext of an
encrypted email. This update mitigates the issue by preventing automatic
loading of external content. (CVE-2017-17689)

Jens Müller, Marcus Brinkmann, Damian Poddebniak, Sebastian Schinzel,
and Jörg Schwenk discovered that PIM Messagelib could be made to leak the
plaintext of S/MIME or PGP encrypted emails. If a user were tricked into
replying to a specially crafted email using an application linked
against PIM Messagelib, an attacker could possibly use this issue to obtain
the plaintext of an encrypted email. (CVE-2019-10732)