rkhunter -- insecure temporary file creation

Gentoo reports:

Sune Kloppenborg Jeppesen and Tavis Ormandy of the Gentoo Linux
Security Team have reported that the check_update.sh script and
the main rkhunter script insecurely creates several temporary
files with predictable filenames.
A local attacker could create symbolic links in the temporary
files directory, pointing to a valid file somewhere on the
filesystem. When rkhunter or the check_update.sh script runs,
this would result in the file being overwritten with the rights of
the user running the utility, which could be the root user.