An issue in the login and reset password functionality of Backdrop CMS v1.22.0 allows attackers to enumerate usernames via password reset requests and distinct responses returned based on usernames.

A Cross-Site Scripting (XSS) vulnerability exists in the node creation form of Backdrop CMS 1.30.

An XSS issue was discovered in Backdrop CMS 1.28.x before 1.28.5 and 1.29.x before 1.29.3. It does not sufficiently validate uploaded SVG images to ensure they do not contain potentially dangerous SVG tags. SVG images can contain clickable links and executable scripting, and using a crafted SVG, it is possible to execute scripting in the browser when an SVG image is viewed. This issue is mitigated by the attacker needing to be able to upload SVG images, and that Backdrop embeds all uploaded SVG images within <img> tags, which prevents scripting from executing. The SVG must be viewed directly by its URL in order to run any embedded scripting.

An XSS issue was discovered in Backdrop CMS 1.28.x before 1.28.5 and 1.29.x before 1.29.3. It doesn't sufficiently isolate long text content when the CKEditor 5 rich text editor is used. This allows a potential attacker to craft specialized HTML and JavaScript that may be executed when an administrator attempts to edit a piece of content. This vulnerability is mitigated by the fact that an attacker must have the ability to create long text content (such as through the node or comment forms) and an administrator must edit (not view) the content that contains the malicious content. This problem only exists when using the CKEditor 5 module.

Backdrop CMS 1.22.0 has Unrestricted File Upload vulnerability via 'themes' that allows attackers to Remote Code Execution.

Backdrop CMS version 1.23.0 was discovered to contain a stored cross-site scripting (XSS) vulnerability via Post content.

Backdrop CMS version 1.23.0 was discovered to contain a stored cross-site scripting (XSS) vulnerability via the Page content.

Backdrop CMS before 1.28.4 and 1.29.x before 1.29.2 allows XSS via an SVG document, if the SVG tag is allowed for a text format.

DISPUTED A stored Cross-site scripting (XSS) issue in Text Editors and Formats in Backdrop CMS before 1.24.2 allows remote attackers to inject arbitrary web script or HTML via the name parameter. When a user is editing any content type (e.g., page, post, or card) as an admin, the stored XSS payload is executed upon selecting a malicious text formatting option. NOTE: the vendor disputes the security relevance of this finding because "any administrator that can configure a text format could easily allow Full HTML anywhere."