Strategic Overview
- Status
- Patched in 3.0.5
- Affected Plugin
- Fathom Analytics for WP
- Affected Version
<= 3.0.4- CVSS
- 4.8Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2021-41836
At a glance
CVE-2021-41836 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Fathom Analytics for WP WordPress plugin, affecting versions <= 3.0.4. It carries a CVSS score of 4.8 (reachable over the network; low attack complexity). The issue is fixed in version 3.0.5; sites on affected versions should update now. Disclosed December 2021, reported by José Aguilera.
Vulnerability Overview
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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Reaching this weakness in Fathom Analytics for WP <= 3.0.4 takes a caller who can reach the endpoint. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.
Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Fathom Analytics for WP the fix is 3.0.5: builds <= 3.0.4 are affected, anything from 3.0.5 onward is not.
Remediation
Update to version 3.0.5, or a newer patched version
How does WordSec protect against this?
The attempt arrives as an ordinary request to Fathom Analytics for WP: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Fathom Analytics for WP 3.0.5 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Related records
Same weakness class
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