---
id: GHSA-993v-76jg-67xr
title: >-
  Duplicate Advisory: Grav: Single invalid UTF-8 byte disables every rule in
  Security::detectXss(), bypassing the page-content XSS safety gate
summary: >-
  Duplicate Advisory: Grav: Single invalid UTF-8 byte disables every rule in
  Security::detectXss(), bypassing the page-content XSS safety gate
severity: medium
cvss: 5.4
cwe:
  - CWE-79
vendor: getgrav
product: getgrav/grav
ecosystem: composer
affected:
  - getgrav/grav < 2.0.14
published: '2026-08-18'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T20:56:29Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-993v-76jg-67xr'
references:
  - url: 'https://github.com/getgrav/grav/security/advisories/GHSA-q2j8-x8hf-63ch'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-75834'
  - url: >-
      https://www.vulncheck.com/advisories/grav-before-stored-xss-via-invalid-utf-8-byte
  - url: 'https://github.com/advisories/GHSA-993v-76jg-67xr'
tags:
  - ghsa
  - composer
ingestedAt: '2026-09-17T21:29:16.994Z'
---

## Overview

### Duplicate Advisory
This advisory has been withdrawn because it is a duplicate of GHSA-q2j8-x8hf-63ch. This link is maintained to preserve external references.

### Original Description
Grav before 2.0.14 contains a stored cross-site scripting vulnerability in the Security::detectXss() function (system/src/Grav/Common/Security.php). All XSS detection patterns use the PCRE /u (UTF-8) modifier, so a single invalid UTF-8 byte anywhere in page content causes preg_match() to return false for every pattern, silently bypassing the save-time XSS safety gate (Validation::checkSafety()). An authenticated attacker with page-edit permissions (without the security.xss_whitelist privilege) can store malicious JavaScript that executes in the browser of a visitor who views the affected page.

## Affected packages

- `getgrav/grav < 2.0.14`

## Remediation

Refer to the advisory for the patched release.