Mixed Content Error when deleting attachements, users from groups, etc

Hi,

if an xwiki instance is served over https, attachments cannot be deleted or, for example, users removed from groups, etc.

The problem is that a mixed-content error occurs here, since these requests are absolutely protocol-inclusive.

A workaround is to perform these actions in a new browser tab.

But how can this error be circumvented? Is it a configuration issue?

Thanks.