A flaw was found in Mozilla. The Mozilla Foundation Security Advisory describes this issue of when an OpenPGP digital signature includes information about the date when the signature was created. When displaying an email that contains a digital signature, it will show the email's date. If the dates were different, Thunderbird didn't report the email as having an invalid signature. If an attacker performs a replay attack, in which an old email with old contents is present at a later time, it could lead the victim to believe that the statements in the email are current. Fixed versions of Thunderbird will require that the signature's date roughly matches the displayed date of the email.