CVE-2021-41836

Name: CVE-2021-41836
Creator: NVD / NIST
Published: 2021-12-14T16:15:09.147+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.8/10EPSS 0.56%

Last modified Jun 17, 2026

CVE-2021-41836 is a medium-severity vulnerability rated 4.8/10 on the CVSS scale. The Fathom Analytics WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and escaping via the $site_id parameter found in the ~/fathom-analytics.php file which allowed attackers with administrative user access to inject arbitrary web scripts, in versions up to and including 3.0.4. This affects multi-site installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.. EPSS estimates a 0.56% chance of exploitation in the next 30 days.

Description

The Fathom Analytics WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and escaping via the $site_id parameter found in the ~/fathom-analytics.php file which allowed attackers with administrative user access to inject arbitrary web scripts, in versions up to and including 3.0.4. This affects multi-site installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.

Metrics

CVSS 3.1

4.8/10

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

0.56%

42.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Conva	Fathom Analytics	<= 3.0.4

References

https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=2641005%40fathom-analytics&new=2641005%40fathom-analytics&sfp_email=&sfph_mail=Patch, Third Party Advisory
https://www.wordfence.com/vulnerability-advisories/#CVE-2021-41836Third Party Advisory
https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=2641005%40fathom-analytics&new=2641005%40fathom-analytics&sfp_email=&sfph_mail=Patch, Third Party Advisory
https://www.wordfence.com/vulnerability-advisories/#CVE-2021-41836Third Party Advisory

Timeline

Published: Dec 14, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-41836?

How severe is CVE-2021-41836?

CVE-2021-41836 has a CVSS score of 4.8/10 (MEDIUM severity). The EPSS model estimates a 0.56% probability of exploitation in the next 30 days.

How do I fix CVE-2021-41836?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-41836?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST