A Cross Site Request Forgery (CSRF) vulnerability exists in Backdrop CMS 1.20, which allows Remote Attackers to gain Remote Code Execution (RCE) on the Hosting Webserver via uploading a maliciously add-on with crafted PHP file. NOTE: the vendor disputes this because the attack requires a session cookie of a high-privileged authenticated user who is entitled to install arbitrary add-ons

An issue was discovered in Backdrop CMS 1.14.x before 1.14.2. It doesn't sufficiently filter output when displaying file type descriptions created by administrators. An attacker could potentially craft a specialized description, then have an administrator execute scripting when viewing the list of file types, aka XSS. This vulnerability is mitigated by the fact that an attacker must have a role with the "Administer file types" permission.

An issue was discovered in Backdrop CMS 1.13.x before 1.13.5 and 1.14.x before 1.14.2. It doesn't sufficiently filter output when displaying certain block descriptions created by administrators. An attacker could potentially craft a specialized description, then have an administrator execute scripting when configuring a layout, aka XSS. This issue is mitigated by the fact that the attacker would be required to have the permission to create custom blocks, which is typically an administrative task.

An issue was discovered in Backdrop CMS 1.13.x before 1.13.5 and 1.14.x before 1.14.2. It allows the upload of entire-site configuration archives through the user interface or command line. It does not sufficiently check uploaded archives for invalid data, allowing non-configuration scripts to potentially be uploaded to the server. This issue is mitigated by the fact that the attacker would be required to have the "Synchronize, import, and export configuration" permission, a permission that only trusted administrators should be given. Other measures in the product prevent the execution of PHP scripts, so another server-side scripting language must be accessible on the server to execute code.

An issue was discovered in Backdrop CMS 1.13.x before 1.13.5 and 1.14.x before 1.14.2. It doesn't sufficiently filter output when displaying content type names in the content creation interface. An attacker could potentially craft a specialized content type name, then have an editor execute scripting when creating content, aka XSS. This vulnerability is mitigated by the fact that an attacker must have a role with the "Administer content types" permission.

Backdrop CMS 1.12.x before 1.12.8 and 1.13.x before 1.13.3 doesn't sufficiently filter output when displaying certain block labels created by administrators. An attacker could potentially craft a specialized label, then have an administrator execute scripting when administering a layout. (This issue is mitigated by the attacker needing permission to create custom blocks on the site, which is typically an administrative permission.)

Backdrop CMS 1.12.x before 1.12.8 and 1.13.x before 1.13.3 allows the upload of entire-site configuration archives through the user interface or command line. It does not sufficiently check uploaded archives for invalid data, potentially allowing non-configuration scripts to be uploaded to the server. (This attack is mitigated by the attacker needing the "Synchronize, import, and export configuration" permission, a permission that only trusted administrators should be given. Other preventative measures in Backdrop CMS prevent the execution of PHP scripts, so another server-side scripting language must be accessible on the server to execute code.) Note: This has been disputed by multiple 3rd parties due to advanced permissions that are needed to exploit.

In Backdrop CMS 1.12.x before 1.12.8 and 1.13.x before 1.13.3, some menu links within the administration bar may be crafted to execute JavaScript when the administrator is logged in and uses the search functionality. (This issue is mitigated by the attacker needing permissions to create administrative menu links, such as by creating a content type or layout. Such permissions are usually restricted to trusted or administrative users.)

Backdrop CMS version 1.11.0 and earlier contains a Cross Site Scripting (XSS) vulnerability in Sanitization of custom class names used on blocks and layouts. that can result in Execution of JavaScript from an unexpected source.. This attack appear to be exploitable via A user must be directed to an affected page while logged in.. This vulnerability appears to have been fixed in 1.11.1 and later.