CVE-2021-41836: Fathom Analytics <= 3.0.4 Authenticated Stored Cross-Site Scripting

Severity: low (CVSS 3.5 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-12-14 · updated 2026-06-17
Weakness: CWE-79

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.

Affected products

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

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