Duplicate Advisory: Grav: XSS Blueprint Validation Bypass via Twig String Concatenation

Overview

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-2c4f-86xc-cr74. This link is maintained to preserve external references.

Original Description

Grav v2.0.0 contains a cross-site scripting vulnerability (fixed in 2.0.1). The XSS blueprint validator (Security::detectXss()) runs on raw page content before Twig processing. When Twig content processing is enabled (twig_content.process_enabled: true), an attacker with page-write API permission can use Twig's string concatenation operator (~) to dynamically construct event handler names, dangerous tag names, or dangerous protocols at render time (e.g. {% set x = "on" ~ "error" %}). The validator sees only the harmless Twig expression and allows the content, but after Twig rendering the output (rendered via {{ page.content|raw }}) contains an active payload such as <img src=1 onerror=alert(1)>, executing arbitrary JavaScript in visitors' browsers.

Affected packages

• getgrav/grav = 2.0.0

Remediation

Refer to the advisory for the patched release.