CVE-2019-19714

Vulnerability

Description

Contao CMS versions 4.8.4 and 4.8.5 suffer from Improper Encoding or Escaping of Output in the login module. The software fails to properly sanitize user-provided input before inserting it into page output, enabling an attacker to inject arbitrary "insert tags" — special placeholders that the CMS evaluates and replaces during rendering [1][2].

Exploitation

Method

An attacker who can submit text to the login module (e.g., via custom fields or crafted parameters) can embed malicious insert tags. No special privileges are required; the attack only needs a way to supply input that the login module processes and later displays. When the page is rendered, the CMS expands these tags without additional validation, executing the attacker's content [3][4].

Impact

Depending on the available insert tags, an attacker could achieve cross-site scripting (XSS), information disclosure, or even remote code execution if certain tags invoke internal functions. The vulnerability essentially turns the login module into an uncontrolled template injection point, with severity rated at CVSS 6.1 (medium) [2].

Mitigation

Users should upgrade to a patched version of Contao CMS (4.8.6 or newer), if available. As of the advisory date, the maintainers have been notified, and the fix involves proper output encoding to prevent insert tag interpretation [3][4]. Systems running the affected builds should apply updates immediately.