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

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

An issue was discovered in Bloop Airmail 3 3.5.9 for macOS. The "send" command in the airmail:// URL scheme allows an external application to send arbitrary emails from an active account. URL parameters for the "send" command with the "attachment_" prefix designate attachment parameters. If the value of an attachment parameter corresponds to an accessible file path, the file is attached to the outbound message. In addition, relative file paths are acceptable attachment parameter values. The handler can be invoked using any method that invokes the URL handler such as a hyperlink in an email. The user is not prompted when the handler processes the "send" command, thus leading to automatic transmission of an email with designated attachments from the target account to a target address.

An issue was discovered in Bloop Airmail 3 3.5.9 for macOS. Its primary WebView instance implements "webView:decidePolicyForNavigationAction:request:frame:decisionListener:" such that requests from HTMLIFrameElements are blacklisted. However, other sub-classes of HTMLFrameOwnerElements are not forbidden by the policy. An attacker may abuse HTML plug-in elements within an email to trigger frame navigation requests that bypass this filter.

An issue was discovered in Bloop Airmail 3 3.5.9 for macOS. Its primary WebView instance implements "webView:decidePolicyForNavigationAction:request:frame:decisionListener:" such that OpenURL is the default URL handler. A navigation request is processed by the default URL handler only if the currentEvent is NX_LMOUSEUP or NX_OMOUSEUP. An attacker may abuse HTML elements with an EventHandler for a chance to validate navigation requests for URLs that are processed during the NX_LMOUSEUP event triggered by clicking an email.