--- A/etc/univention/templates/files/etc/apache2/sites-available/univention-letsencrypt.conf     2023-02-22 21:54:20.463097949 +0100
+++ B/etc/univention/templates/files/etc/apache2/sites-available/univention-letsencrypt.conf     2023-12-31 14:40:58.694411057 +0100
@@ -27,6 +27,12 @@
        domains = []
 
 if configRegistry.is_true('letsencrypt/services/apache2'):
+       try:
+               with open('/etc/univention/templates/files/etc/apache2/sites-available/ssl.d/10hsts') as fd:
+                       hsts = run_filter(fd.read(), configRegistry).decode('UTF-8').replace('\n','\n\t')
+       except IOError:
+               hsts = ''
+
        for domain in domains:
                if domain == fqdn:
                        continue
@@ -51,12 +57,14 @@
        SSLCertificateKeyFile {key}
 
        {docker_apps_reverse_proxy}
+       {hsts}
 
 </VirtualHost>""".format(
                        domain=domain,
                        cert=cert_path,
                        key=key_path,
-                       docker_apps_reverse_proxy = docker_apps_reverse_proxy
+                       docker_apps_reverse_proxy=docker_apps_reverse_proxy,
+                       hsts=hsts,
                ))
 @!@
 </IfModule>