Date: 
Wednesday, Sep 30th, 2020
Advisory ID: 
BACKDROP-SA-CORE-2020-005
Security risk: 
Moderately Critical
Vulnerability: 
Cross Site Scripting
CVE ID: 
CVE-2020-13666
Versions affected: 
  • Backdrop Core 1.17.x versions prior to 1.17.1
  • Backdrop Core 1.16.x versions prior to 1.16.4

Backdrop versions 1.15 and prior do not receive security coverage.

Description: 

The Backdrop AJAX API does not disable JSONP by default, which can lead to cross-site scripting.

This SA is equivalent to Drupal core - Moderately critical - Cross-site scripting - SA-CORE-2020-007

Solution: 

Upgrade your site to the most recent version of Backdrop core. Download available on the Backdrop CMS 1.17.1 release page. See the update instructions, if needed.

If you were previously relying on Backdrop's AJAX API to perform trusted JSONP requests, you'll either need to override the AJAX options to set "jsonp: true", or you'll need to use the jQuery AJAX API directly.

If you are using jQuery's AJAX API for user-provided URLs in a contrib or custom module, you should review your code and set "jsonp: false" where this is appropriate.

All Backdrop sites should also pass such URLs through the new Drupal.sanitizeAjaxUrl() function.

Reported By: 
Fixed By: 

Security email list

Backdrop maintains a security mailing list. Whenever a security release comes out, an email will be sent to everyone subscribed to that list, announcing the new release. Please follow the steps below to join the Security email list.

  1. Log in to backdropcms.org
  2. Edit your profile
  3. Switch to the "Subscriptions" tab
  4. Check the box labeled "Security updates"
  5. Save the form