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CRITICAL severity

CVE-2016-8869 — joomla-cms

CRITICALFix: joomla/joomla-cms@bae1d43

CVE-2016-8869 is a critical-severity (CVSS 9.8) Improper Input Validation vulnerability. 8 public exploit references exist, so weaponization risk is real. A fix is available — see the affected versions and patch details below.

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
8 known
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
97.3%probability of exploitation in next 30 days
Very High Risk-0.17%
Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk
90.3%93.2%96.1%99.1%93.4%97.3%Apr 26Jul 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2016-8869 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.

Description

The register method in the UsersModelRegistration class in controllers/user.php in the Users component in Joomla! before 3.6.4 allows remote attackers to gain privileges by leveraging incorrect use of unfiltered data when registering on a site.

Affected Products

1 product · 1 configurations
Application
joomla\!joomla
≤ 3.6.3
range
Exploits & PoCs
8

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-40637webappsphp

Joomla! 3.4.4 < 3.6.4 - Account Creation / Privilege Escalation

by Xiphos Research Ltd · Oct 27, 2016

Exploit-DB Source

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Fix

    Upgrade the affected component to the fixed release for CVE-2016-8869, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

The register method in the UsersModelRegistration class in controllers/user.php in the Users component in Joomla! before 3.6.4 allows remote attackers to gain privileges by leveraging incorrect use of unfiltered data when registering on a site.
O3 Security · Impact-Aware SCA

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CVE-2016-8869: joomla-cms (Critical 9.8)