Debian Security Advisory DSA 978-1 – Tavis Ormandy noticed that gnupg, the GNU privacy guard – a free PGP replacement, verifies external signatures of files successfully even though they don’t contain a signature at all.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/43989/dsa-978-1.txt
Source: https://packetstormsecurity.com/files/43989/Debian-Linux-Security-Advisory-978-1.html