gtkdiskfree is a GTK-based GUI to show free disk space.
Eric Romang discovered that gtkdiskfree insecurely creates a predictable temporary file to handle command output.
A local attacker could create a symbolic link in the temporary files directory, pointing to a valid file somewhere on the filesystem. When gtkdiskfree is executed, this would result in the file being overwritten with the rights of the user running the application.
There is no known workaround at this time.
All gtkdiskfree users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=app-admin/gtkdiskfree-1.9.3-r1"