Problem:
The shortcode [wpml_language_selector_widget] used for showing the language switcher in the header includes the path to the CSS file like so "sitepress-multilingual-cms/templates/language-switchers/legacy-list-horizontal/style.css?ver=1" It is missing the HTTP or HTTPS part, which can cause a security issue.
Solution:
Our developers checked this issue and concluded that there was no security risk by not having the HTTP or HTTPS part in the CSS URL link, and it should not be included due to a specific reason.