Horizon Alert
Summary of the vulnerability and why it matters
This issue in Concrete CMS allows an attacker with editor privileges to inject malicious code through the height parameter, which is not properly checked. This could lead to JavaScript executing in visitors' browsers, potentially stealing credentials or hijacking sessions.
- Attack requires editor access.
- Malicious code runs in visitor browsers.
- Can lead to credential theft.
Attack Path
How an attacker could exploit the issue
An attacker with editor privileges in Concrete CMS can inject malicious JavaScript into the height parameter of content. This stored XSS payload will execute in the browser of any user viewing that content, enabling actions like session hijacking or credential theft.
- Requires editor privileges.
- Targets content height parameter.
- JavaScript executes in visitor browsers.
Live Threat
Current exploitation, exposure, and threat context
This stored XSS vulnerability in Concrete CMS, while requiring editor privileges, affects a web application often exposed externally. Attackers could potentially leverage this to inject malicious scripts into pages, impacting users who view them. The vulnerability is relatively recent, and a public exploit is not yet confirmed.
- Public exploit not yet confirmed.
- Requires editor privileges.
- Affects internet-facing applications.
Priority actions
Operational Fix
Recommended remediation, mitigation, and detection steps
Prioritize reviewing logs for unauthorized content modifications or user privilege escalations, as this stored XSS vulnerability can be exploited by users with editor privileges. Block traffic originating from known malicious IPs that may be attempting to leverage this weakness, and identify all Concrete CMS instances running version 9.5.0 or below for potential patching or isolation.
- Upgrade Concrete CMS to version 9.5.1.
- Isolate or disable affected instances.
- Monitor for suspicious JavaScript execution.
