CVE-2026-75834

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.

CVSS Vector

References

• https://github.com/getgrav/grav/security/advisories/GHSA-q2j8-x8hf-63ch
• https://www.vulncheck.com/advisories/grav-before-stored-xss-via-invalid-utf-8-byte