Package Instance

Improper Access Control
Under certain circumstances, the Drupal core form API evaluates form element access incorrectly. This may lead to a user being able to alter data they should not have access to. No forms provided by Drupal core are known to be vulnerable. However, forms added through contributed or custom modules or themes may be affected.

Improper access control
In some situations, the Image module does not correctly check access to image files not stored in the standard public files directory when generating derivative images using the image styles system. Access to a non-public file is checked only if it is stored in the "private" file system. However, some contributed modules provide additional file systems, or schemes, which may lead to this vulnerability. This vulnerability is mitigated by the fact that it only applies when the site sets (Drupal 9) $config['image.settings']['allow_insecure_derivatives'] or (Drupal 7) $conf['image_allow_insecure_derivatives'] to TRUE. The recommended and default setting is FALSE, and Drupal core does not provide a way to change that in the admin UI. Some sites may require configuration changes following this security release. Review the release notes for your Drupal version if you have issues accessing files or image styles after updating.

Lack of domain validation in Druple core
The Media oEmbed iframe route does not properly validate the iframe domain setting, which allows embeds to be displayed in the context of the primary domain. Under certain circumstances, this could lead to cross-site scripting, leaked cookies, or other vulnerabilities.

Unrestricted Upload of File with Dangerous Type
Drupal core sanitizes filenames with dangerous extensions upon upload (reference: SA-CORE-2020-012) and strips leading and trailing dots from filenames to prevent uploading server configuration files (reference: SA-CORE-2019-010). However, the protections for these two vulnerabilities previously does not work correctly together. As a result, if the site were configured to allow the upload of files with an htaccess extension, these files' filenames would not be properly sanitized. This could allow bypassing the protections provided by Drupal core's default .htaccess files and possible remote code execution on Apache web servers. This issue is mitigated by the fact that it requires a field administrator to explicitly configure a file field to allow htaccess as an extension (a restricted permission), or a contributed module or custom code that overrides allowed file uploads.