FreeBSD Security Advisory FreeBSD-SA-04:01.mksnap_ffs – The mksnap_ffs command creates a snapshot of a filesystem. A snapshot is a static representation of the state of the filesystem at a particular point in time. The kernel interface for creating a snapshot of a filesystem is the same as that for changing the flags on that filesystem. Due to an oversight, the mksnap_ffs command called that interface with only the snapshot flag set, causing all other flags to be reset to the default value.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/32597/FreeBSD-SA-04%3A01.mksnap_ffs
Source: https://packetstormsecurity.com/files/32597/FreeBSD-Security-Advisory-2004.1.html