CVE-2020-8421 Cross-site scripting in n/a
Cross-site scripting vulnerability in Joomla allows attackers to inject malicious scripts via usernames, potentially leading to session hijacking or code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2020-8421?
CVE-2020-8421 is a medium-severity cross-site scripting vulnerability in Joomla Joomla\!, published on 28 Jan 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
An issue was discovered in Joomla! before 3.9.15. Inadequate escaping of usernames allows XSS attacks in com_actionlogs.
Weakness: CWE-79
Which versions are affected by CVE-2020-8421?
1 open source package ship an affected version, including joomla. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
joomla Bitnami | From 3.9.0 | 3.9.14 |
Products include Joomla Joomla\!.
How do I fix CVE-2020-8421?
Upgrade joomla to 3.9.14 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2020-8421 being exploited?
There is no known exploitation of CVE-2020-8421 in the wild and no public exploit code.
Other vulnerabilities in Joomla Joomla\!
- CVE-2016-10033 PHPMailer Command Injection
- CVE-2023-23752 Joomla! Improper Access Control
- CVE-2026-48902 Joomla! Core - [20260518] - Transport encryption downgrade for password and username reset links
- CVE-2025-25226 [20250401] - Joomla Framework - SQL injection vulnerability in quoteNameStr method of Database package
- CVE-2022-23795 [20220303] - Core - User row are not bound to a authentication mechanism
Sources
Also known as BIT-joomla-2020-8421, GHSA-m4hj-w5c6-qqv3.