PGP Desktop 10.0.x before 10.0.3 SP2 and 10.1.0 before 10.1.0 SP1 does not properly implement the "Decrypt/Verify File via Right-Click" functionality for multi-packet OpenPGP messages that represent multi-message input, which allows remote attackers to spoof signed data by concatenating an additional message to the end of a legitimately signed message, related to a "piggy-back" or "unsigned data injection" issue.
https://pgp.custhelp.com/app/answers/detail/a_id/2290
https://exchange.xforce.ibmcloud.com/vulnerabilities/63366
https://euvd.enisa.europa.eu/vulnerability/EUVD-2010-3614
http://www.securitytracker.com/id?1024760
http://www.kb.cert.org/vuls/id/300785
http://www.cs.ru.nl/E.Verheul/papers/Govcert/Pretty%20Good%20Piggybagging%20v1.0.pdf