CVE-2026-57829 is a high-severity vulnerability in the Helix Ultimate extension for Joomla, identified as CWE-79 (Improper Neutralization of Input During Web Page Generation). It allows unauthenticated attackers to perform stored cross-site scripting (XSS) attacks by injecting malicious code that is stored and later executed in the context of users visiting the affected Joomla site. The vulnerability affects versions from 1.0 up to and including 2.2.6. No official patch or remediation level has been published at this time.

Successful exploitation of this vulnerability could allow attackers to execute arbitrary scripts in the browsers of users visiting the affected Joomla sites. This can lead to session hijacking, defacement, or redirection to malicious sites. Since the vulnerability is unauthenticated and stored, it poses a significant risk to site visitors and administrators.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, consider applying temporary mitigations such as input validation or output encoding if feasible. Monitor official joomshaper.com communications for updates on patches or workarounds.