Cleartext Transmission of Sensitive Information
An issue was discovered in Enigmail before 1.9.9. A remote attacker can obtain cleartext content by sending an encrypted data block (that the attacker cannot directly decrypt) to a victim, and relying on the victim to automatically decrypt that block and then send it back to the attacker as quoted text, aka the TBE-01-005 "replay" issue.
CWE-319 - Cleartext Transmission of Sensitive Information
The software transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.