Decidim is a participatory democracy framework. Starting in version 0.23.0 and prior to versions 0.27.5 and 0.28.0, the CSRF authenticity token check is disabled for the questionnaire templates preview. The issue does not imply a serious security thread as you need to have access also to the session cookie in order to see this resource. This URL does not allow modifying the resource but it may allow malicious users to gain access to information which was not meant to be public. The issue is fixed in version 0.27.5 and 0.28.0. As a workaround, disable the templates functionality or remove all available templates.
Vulmon