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CVE-2026-25900 Joomla! Project CVE debrief

CVE-2026-25900 is a cross-site scripting (XSS) vulnerability in Joomla core feed modules, published 2026-05-26. The vulnerability stems from lack of output escaping, allowing crafted input to execute scripts in a victim's browser. CVSS 4.0 vector indicates network attack vector with low attack complexity, requiring high privileges and user interaction, with high confidentiality impact and low integrity/availability impact. The vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation). Joomla's security team published advisory 20260501 addressing this core issue. No known exploitation in ransomware campaigns (non-KEV). Organizations using Joomla feed modules should apply vendor patches when available and implement output encoding controls.

Vendor
Joomla! Project
Product
Joomla! CMS
CVSS
MEDIUM 6.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-26
Original CVE updated
2026-07-20
Advisory published
2026-05-26
Advisory updated
2026-07-20

Who should care

Joomla site administrators, web application security teams, content management system operators, security auditors assessing Joomla deployments

Technical summary

Cross-site scripting vulnerability in Joomla core feed modules caused by insufficient output escaping. Attack vector requires high privileges and user interaction. Confidentiality impact rated high per CVSS 4.0.

Defensive priority

medium

Recommended defensive actions

  • Apply Joomla security update for advisory 20260501 when available from vendor
  • Review feed module output encoding implementations for proper HTML entity encoding
  • Implement Content Security Policy headers to mitigate XSS impact
  • Audit feed module configurations for unauthorized modifications
  • Monitor for anomalous script injection attempts in feed content submissions

Evidence notes

CVE description confirms XSS via lack of output escaping in feed modules. CVSS 4.0 vector from NVD: AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:L/VA:L. CWE-79 classification from [email protected]. Vendor attribution supported by Joomla security advisory reference.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-25900 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-25900

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-25900 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-25900

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.