I have LimeSurvey installed on a mutualised server since 3 years, and I can use different subdomains linked to my installation: enquetes.domain1.fr, enquetes.domain2.fr, enquetes.domain3.com... Since I upgraded to 6.17.11+260706, I still can connect to the list of questionnaires on enquetes.domain2.fr, enquetes.domain3.com, but I cannot connect to Admin interface from enquetes.domain2.fr/admin or enquetes.domain3.com/admin, only from enquetes.domain1.fr/admin. A 400 error "Bad request" page is displayed, with LimeSurvey logo on the right. I added secondary domains to application/config/allowed_hosts.php with no success. Any idea of how I should solve this problem? Thank you!

When last upgrade happens, you have an alert about this situation.

How do you add your allowed host ?

You can set it too in config.php file :  www.limesurvey.org/manual/Optional_settings/en#Host_control

Hi Denis, thank you very much for your help.
I must admit I didn't pay attention to the alert... I will, next time.
I verified my allowed hosts file, and noticed that there was an error in the lines I had added. Now that it is corrected, I can use every domains.
Sorry for wasting your time and many thanks for your precious work on LimeSurvey!