In Drupal versions 8.4.x versions before 8.4.5 the Settings Tray module has a vulnerability that allows users to update certain data that they do not have the permissions for. If you have implemented a Settings Tray form in contrib or a custom module, the correct access checks should be added. This release fixes the only two implementations in core, but does not harden against other such bypasses. This vulnerability can be mitigated by disabling the Settings Tray module.

The Subuser module before 6.x-1.8 for Drupal does not properly check "switch subuser" permissions, which allows remote authenticated parent users to change their role by switching to a subuser they created.

The Mime Mail module 6.x-1.x before 6.x-1.1 for Drupal does not properly restrict access to files outside Drupal's publish files directory, which allows remote authenticated users to send arbitrary files as attachments.

An issue was discovered in Http Foundation in Symfony 2.7.0 through 2.7.48, 2.8.0 through 2.8.43, 3.3.0 through 3.3.17, 3.4.0 through 3.4.13, 4.0.0 through 4.0.13, and 4.1.0 through 4.1.2. It arises from support for a (legacy) IIS header that lets users override the path in the request URL via the X-Original-URL or X-Rewrite-URL HTTP request header. These headers are designed for IIS support, but it's not verified that the server is in fact running IIS, which means anybody who can send these requests to an application can trigger this. This affects \Symfony\Component\HttpFoundation\Request::prepareRequestUri() where X-Original-URL and X_REWRITE_URL are both used. The fix drops support for these methods so that they cannot be used as attack vectors such as web cache poisoning.

Cross-site scripting (XSS) vulnerability in the MAYO theme 7.x-1.x before 7.x-1.3 for Drupal allows remote authenticated users with the "administer themes" permission to inject arbitrary web script or HTML via vectors related to header background setting.