Backdrop Cross-site Scripting

Backdrop CMS version 1.23.0 was discovered to contain a stored cross-site scripting (XSS) vulnerability via 'Comment.' . (2022-11-22, CVE-2022-42097)

Backdrop CMS version 1.23.0 was discovered to contain a stored cross-site scripting (XSS) vulnerability via the 'Card' content. (2022-11-22, CVE-2022-42094)

A stored cross-site scripting (XSS) vulnerability in the Add Link function of BackdropCMS v1.21.1 allows attackers to execute arbitrary web scripts or HTML. (2022-02-15, CVE-2022-24590)

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.) (2019-08-08, CVE-2019-14769)

Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.

The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:

https://server.com/confirmation?message=Transaction+Complete

what results in:

<span>Confirmation: Transaction Complete</span>

In that case the message can be modified to become a valid Javascript code, e.g.:

https://server.com/confirmation?message=<script>dangerous javascript code here</script>

and it will be executed locally by the user's browser with full access to the user's personal application/browser data:

<span>Confirmation: <script>dangerous javascript code here</script></span>