DSA-4123-1

Drupal 8.4.x versions before 8.4.5 and Drupal 7.x versions before 7.57 has a Drupal.checkPlain() JavaScript function which is used to escape potentially dangerous text before outputting it to HTML (as JavaScript output does not typically go through Twig autoescaping). This function does not correctly handle all methods of injecting malicious HTML, leading to a cross-site scripting vulnerability under certain circumstances. The PHP functions which Drupal provides for HTML escaping are not affected.

Drupal core 7.x versions before 7.57 when using Drupal's private file system, Drupal will check to make sure a user has access to a file before allowing the user to view or download it. This check fails under certain conditions in which one module is trying to grant access to the file and another is trying to deny it, leading to an access bypass vulnerability. This vulnerability is mitigated by the fact that it only occurs for unusual site configurations.

A jQuery cross site scripting vulnerability is present when making Ajax requests to untrusted domains. This vulnerability is mitigated by the fact that it requires contributed or custom modules in order to exploit. For Drupal 8, this vulnerability was already fixed in Drupal 8.4.0 in the Drupal core upgrade to jQuery 3. For Drupal 7, it is fixed in the current release (Drupal 7.57) for jQuery 1.4.4 (the version that ships with Drupal 7 core) as well as for other newer versions of jQuery that might be used on the site, for example using the jQuery Update module.

Drupal core 7.x versions before 7.57 has an external link injection vulnerability when the language switcher block is used. A similar vulnerability exists in various custom and contributed modules. This vulnerability could allow an attacker to trick users into unwillingly navigating to an external site.