A vulnerability affecting GnuPG has made some of the widely used email encryption software vulnerable to digital signature spoofing for many years. The list of affected programs includes Enigmail and GPGTools.
About the vulnerability (CVE-2018-12020)
CVE-2018-12020, dubbed “SigSpoof” by Marcus Brinkmann, the researcher which found it, arises from “weak design choices.”
“The signature verification routine in Enigmail 184.108.40.206, GPGTools 2018.2, and python-gnupg 0.4.2 parse the output of GnuPG 2.2.6 with a “–status-fd 2” option, which allows remote attackers to spoof arbitrary signatures via the embedded “filename” parameter in OpenPGP literal data packets, if the user has the verbose option set in their gpg.conf file,” Brinkmann explained.