Maintenance of ILIAS version 5.3 has ended with release 5.3.23 in August this year. There will be no more security fixes for the 5.3 branch. So no, these fixes have not been backported to 5.3.
See the release notes for more information:
https://docu.ilias.de/goto_docu_pg_124766_35.html
See the release notes for more information:
https://docu.ilias.de/goto_docu_pg_124766_35.html