lwp-download in libwww-perl before 5.835 does not reject downloads to filenames that begin with a . (dot) character, which allows remote servers to create or overwrite files via (1) a 3xx redirect to a URL with a crafted filename or (2) a Content-Disposition header that suggests a crafted filename, and possibly execute arbitrary code as a consequence of writing to a dotfile in a home directory.
CWE-20