API call does not work anymore after update to Nextcloud 28


I have developed a Nextcloud plugin for the monitoring solution CheckMK (see Checkmk Exchange).
Currently I’m adapting this plugin to changes in version 28 and I’m experiencing a strange problem:

If I run the script which gathers all the Nextcloud information from the command line, it works fine.
If I run the script from within the Web GUI of CheckMK, it fails with 401 error (“not authorized”). And if I click on the link which is presented by the error message, then I get the message ‘{“error”:“Strict cookie has not been found in request”}’.

I have tried several approaches with setting the “SameSite”-Cookie to “Strict”, but nothing was successfull. I even don’t know whether I’m working ih the right direction here…

Does anyone know about some minor changes with version 28 when requesting the API of Nextcloud, especially what cookies are concerned?

And please excuse me to create this topic here, maybe it is a CheckMK related problem. But the plugin worked for all version of Nextcloud from 25 onwards with all versions/editions of CheckMK - until now.

Best regards


By the way: All my Nextcloud installations are based on the official docker image.