concrete5 8.1.0 places incorrect trust in the HTTP Host header during caching, if the administrator did not define a "canonical" URL on installation of concrete5 using the "Advanced Options" settings. Remote attackers can make a GET request with any domain name in the Host header; this is stored and allows for arbitrary domains to be set for certain links displayed to subsequent visitors, potentially an XSS vector.
Multiple cross-site scripting (XSS) vulnerabilities in concrete5 5.7.2.1, 5.7.2, and earlier allow remote attackers to inject arbitrary web script or HTML via the (1) gName parameter in single_pages/dashboard/users/groups/bulkupdate.php or (2) instance_id parameter in tools/dashboard/sitemap_drag_request.php.
Cross-site scripting (XSS) vulnerability in single_pages\download_file.php in concrete5 before 5.6.3 allows remote attackers to inject arbitrary web script or HTML via the HTTP Referer header to index.php/download_file.