Version 5.4.0 was released on August 16th. Please update it in portage. Thank you.
commit 8fd16dbf1f58539d9007b52b89829d08ef715425 Author: Sam Jorna <wraeth@gentoo.org> Commit: Sam Jorna <wraeth@gentoo.org> app-arch/rar: bump to 5.4.0 Gentoo-bug: 592224 Package-Manager: portage-2.3.3