|Postfix before 2.3.15, 2.4 before 2.4.8, 2.5 before 2.5.4, and 2.6
before 2.6-20080814, when the operating system supports hard links to
symlinks, allows local users to append e-mail messages to a file to
which a root-owned symlink points, by creating a hard link to this
symlink and then sending a message. NOTE: this can be leveraged to
gain privileges if there is a symlink to an init script.