Security Advisories

JavaScript cross-site scripting prevention is incomplete - Critical

Backdrop has a Backdrop.checkPlain() JavaScript function which is used to escape potentially dangerous text before outputting it to HTML. 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 Backdrop provides for HTML escaping are not affected.

This module enables you to upload files to fields via several sources.

The module doesn't sufficiently handle access control under the scenario of the autocomplete path of reference sources.

The Captcha module enables you to use various techniques to block automated scripts / robots from submitting content to a site, e.g. to block spam comments.

The module doesn't properly store the session ID of visitors who are given a session which could lead to a Denial of Service attack.

This vulnerability is mitigated by the fact that Backdrop does not give a session to all visitors, especially when used with advanced caching systems like Varnish.

Access Bypass - Moderately Critical

When creating a view, you can optionally use Ajax to update the displayed data via filter parameters. The views subsystem/module did not restrict access to the Ajax endpoint to only views configured to use Ajax. This is mitigated if you have access restrictions on the view, however, many widely used contrib modules don't have access restrictions set on the default views they provide. Any view that does not have access controls on the default (master) display may be vulnerable. The vulnerability does not require any authentication to be exploited. A successful exploit results in some non-public data being made public.

Sites running versions of Backdrop prior to 1.x-1.7.2 should update immediately.

It is best practice to always include some form of access restrictions on all views, even if you are using another module to display them.

The Search 404 module enables you to redirect 404 pages to a search page on the site for the keywords in the url that was not found.

The module did not filter administrator-provided text before displaying it to the user on the 404 page creating a Cross Site Scripting (XSS) vulnerability.

This vulnerability is mitigated by the fact that an attacker must have a role with the permission "administer search".

The module doesn't sufficiently sanitize column names provided by the client when they are querying for data and trying to sort it.  

This vulnerability is mitigated by the fact that a site must have an "Index" resource enabled and the attacker must know the endpoint's URL.

This SMTP module enables you to send mail using a third party (non-system) mail service instead of the local system mailer included with Backdrop. When this module is in debugging mode, it will log privileged information.

Files uploaded by anonymous users into a private file system can be accessed by other anonymous users - access bypass - Moderately Critical

Private files that have been uploaded by an anonymous user but not permanently attached to content on the site should only be visible to the anonymous user that uploaded them, rather than all anonymous users. Backdrop core did not previously provide this protection, allowing an access bypass vulnerability to occur. This issue is mitigated by the fact that in order to be affected, the site must allow anonymous users to upload files into a private file system.

The Drupal security team has also received reports that this vulnerability is being exploited for spam purposes, similar to the scenario discussed in PSA-2016-003 for the public file system.

Access bypass via views of taxonomy terms

The Backdrop core module Views allows site builders to create listings of various data in the Backdrop database.

The Views module fails to add the required query tags to listings of Taxonomy Terms, which could cause private data stored on Taxonomy Terms to be leaked to users without permission to view it.

This is mitigated by the fact that a View must exist that lists Taxonomy Terms which contain private data. If all the data on Taxonomy Terms is public or there are no applicable Views, then your site is unaffected.

Access bypass via views bulk operations on user accounts

The Backdrop core user account listing allows administration of user accounts. The bulk operation on this page that allows additional roles to be added to accounts also allowed a user to promote themselves beyond their intended access. 

This is mitigated by the fact that a user must already have permission to view the user account page in order to have access to the bulk operation.

This module provides a standardized solution for building API's so that external clients can communicate with Backdrop.

The module accepts user submitted data in PHP's serialization format ("Content-Type: application/vnd.php.serialized") which can lead to arbitrary remote code execution.

This vulnerability is mitigated by the fact that an attacker must know your Service Endpoint's path, and your Service Endpoint must have "application/vnd.php.serialized" enabled as a request parser.