Exposure of Sensitive Information to an Unauthorized Actor

Summary

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.