eM Client before 7.2.33412.0 automatically imported S/MIME certificates and thereby silently replaced existing ones. This allowed a man-in-the-middle attacker to obtain an email-validated S/MIME certificate from a trusted CA and replace the public key of the entity to be impersonated. This enabled the attacker to decipher further communication. The entire attack could be accomplished by sending a single email.

S/MIME: CBC gadget attacks allows to exfiltrate plaintext out of encrypted emails

The S/MIME specification allows a Cipher Block Chaining (CBC) malleability-gadget attack that can indirectly lead to plaintext exfiltration, aka EFAIL.

OpenPGP: CFB gadget attacks allows to exfiltrate plaintext out of encrypted emails

The OpenPGP specification allows a Cipher Feedback Mode (CFB) malleability-gadget attack that can indirectly lead to plaintext exfiltration, aka EFAIL. NOTE: third parties report that this is a problem in applications that mishandle the Modification Detection Code (MDC) feature or accept an obsolete packet type, not a problem in the OpenPGP specification