What is efail?
Efail is the name given by German Researchers to a potential attack against PGP or S/MIME encoded emails to take the encrypted contents and send them to a third-party actor.
How does efail work?
Efail requires an HTML encoded email to be manipulated by prepending an html image tag to the beginning of the email. This in turn forces the email client to send a request to a malicious domain looking for an image file that is the body of the encrypted email. Read more