CVE-2019-14769 in Backdrop
Summary
by MITRE
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.)
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Analysis
by VulDB Data Team • 11/21/2023
Backdrop CMS versions 1.12.x prior to 1.12.8 and 1.13.x prior to 1.13.3 contain a vulnerability in their block label handling mechanism that constitutes a cross-site scripting flaw. This vulnerability exists within the administrative interface where block labels are rendered and displayed to users with appropriate permissions. The issue stems from insufficient output filtering mechanisms that fail to properly sanitize user-controlled data when displaying block labels within the content management interface. When an administrator views a page layout containing specially crafted block labels, the malicious content can execute within the administrator's browser context, creating a potential vector for privilege escalation or session hijacking attacks.
The technical flaw manifests in the rendering process of block labels within Backdrop CMS's administrative panels. Specifically, when administrators access layout management interfaces, the system displays block labels without adequate sanitization of potentially malicious input. This represents a classic cross-site scripting vulnerability categorized under CWE-79, which defines the weakness as the failure to sanitize output that is then interpreted by web browsers as executable code. The vulnerability requires an attacker to possess permissions to create custom blocks, which typically aligns with administrative or content management roles within the CMS ecosystem. This permission requirement acts as a mitigating factor but does not eliminate the risk entirely, as the attack vector remains viable when attackers can compromise administrative accounts or when the application's permission model is misconfigured.
The operational impact of this vulnerability extends beyond simple script execution as it enables attackers to potentially escalate privileges and gain unauthorized access to administrative functions. An attacker who successfully crafts a malicious block label could potentially steal administrator sessions, modify content, or manipulate the CMS configuration to establish persistent access. The attack chain typically involves the attacker creating a specially crafted block label containing malicious javascript, which then executes when the administrator views the layout page. This vulnerability directly maps to ATT&CK technique T1059.007 for command and scripting interpreter, and T1548.001 for abuse of privileges, as it allows for code execution within the context of administrative users. The vulnerability affects the integrity and confidentiality of the CMS environment, potentially enabling data exfiltration and unauthorized modifications to the website's content and configuration.
Mitigation strategies for this vulnerability include immediate application of the patched versions 1.12.8 and 1.13.3, which implement proper output filtering mechanisms for block labels. Organizations should also implement principle of least privilege by restricting block creation permissions to only essential administrative users. Additional protective measures include regular security audits of custom blocks, implementing content security policies to prevent script execution, and monitoring administrative interfaces for suspicious activity. The patch addresses the core issue by sanitizing user input before rendering block labels in administrative contexts, ensuring that potentially malicious content cannot be executed when administrators view layout configurations. Security teams should also consider implementing web application firewalls to detect and block suspicious block label content, and conduct regular training for administrators on recognizing potential social engineering attacks that might exploit this vulnerability.