PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-48905 Joomla! Project CVE debrief

A cross-site scripting (XSS) vulnerability exists in Joomla! due to inadequate input filtering within the HTML filter's cleanAttributes code. The flaw allows attackers with high privileges to inject malicious scripts through insufficiently sanitized content, potentially compromising user sessions or executing unauthorized actions in victims' browsers. The vulnerability affects Joomla! versions 3.0.0 through 5.4.5 and 6.0.0 through 6.0.x, with fixes available in versions 5.4.6 and 6.1.0. This issue was disclosed by the Joomla! Security Strike Team on May 20, 2026, and published to NVD on May 26, 2026.

Vendor
Joomla! Project
Product
Joomla! Framework Filter package
CVSS
MEDIUM 6.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-26
Original CVE updated
2026-05-26
Advisory published
2026-05-26
Advisory updated
2026-05-26

Who should care

Joomla! site administrators, security teams managing content management systems, web application developers implementing HTML sanitization, and organizations with Joomla! deployments in production environments

Technical summary

The vulnerability stems from insufficient input validation in the cleanAttributes method of Joomla!'s HTML filter code. An attacker with high-level privileges (PR:H) can craft malicious content that bypasses filtering controls, resulting in stored or reflected XSS when rendered in user browsers. The CVSS 4.0 score of 6.9 (MEDIUM) reflects the high privilege requirement and user interaction dependency, though successful exploitation yields high confidentiality impact. The fix implements improved attribute sanitization logic in the framework's filtering components.

Defensive priority

medium

Recommended defensive actions

  • Apply Joomla! updates to version 5.4.6 or 6.1.0 or later to remediate the inadequate content filtering vulnerability
  • Review and audit content filtering configurations in Joomla! HTML filter implementations
  • Implement defense-in-depth with Content Security Policy headers to mitigate XSS impact
  • Monitor for unauthorized script execution in administrative and content management interfaces
  • Validate that third-party extensions using Joomla! HTML filtering are updated to compatible patched versions

Evidence notes

CVE published 2026-05-26T17:16:55.323Z; modified 2026-05-26T20:51:16.700Z. Vendor advisory dated 20260520. CVSS 4.0 vector indicates network attack vector, low attack complexity, high privileges required, user interaction required, with high confidentiality impact and low integrity/availability impact. CPE ranges confirm affected versions: 3.0.0 to <5.4.6 and 6.0.0 to <6.1.0. CWE-79 (Improper Neutralization of Input During Web Page Generation) classified as primary weakness.

Official resources

2026-05-26