The signature of a digitally signed S/MIME email message may optionally specify the signature creation date and time

The signature of a digitally signed S/MIME email message may optionally specify the signature creation date and time. If present, Thunderbird did not compare the signature creation date with the message date and time, and displayed a valid signature despite a date or time mismatch. This could be used to give recipients the impression that a message was sent at a different date or time. This vulnerability affects Thunderbird < 115.6.