Security readout for executives and security teams
Plain-English summary
CVE-2021-41836 is a stored cross-site scripting issue in the Fathom Analytics WordPress plugin through version 3.0.4. An administrator-level user could save script content through the site ID setting when normal HTML filtering was disabled. Business impact is mainly account, content, and trust risk inside affected WordPress administration contexts.
Executive priority
Treat this as a moderate-priority WordPress hygiene issue, not an emergency based on the provided evidence. Prioritize sites with many administrators, multisite deployments, or sensitive authenticated users. Resolve during the next maintenance cycle unless suspicious admin activity is found.
Technical view
The plugin insufficiently validated and escaped the $site_id parameter in fathom-analytics.php, enabling authenticated stored XSS. The CVSS 3.1 score is 4.8 with high privileges required, user interaction required, changed scope, and low confidentiality and integrity impact. Sources identify affected versions up to and including 3.0.4.
Likely exposure
Exposure is limited to WordPress sites running the Fathom Analytics plugin version 3.0.4 or earlier. The source specifically notes multisite installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.
Exploitation context
The bundle does not show KEV listing or cited active exploitation. Exploitation requires authenticated administrative access and user interaction, which reduces broad internet-scale risk. The stored nature still matters because malicious script can persist and execute later in trusted WordPress contexts.
Researcher notes
Key constraints are high required privileges and affected configurations involving disabled unfiltered_html. The source bundle identifies the vulnerable parameter and file, but does not provide active exploitation evidence or detailed fixed-version notes beyond affected versions through 3.0.4.
Mitigation direction
- Inventory WordPress sites for the Fathom Analytics plugin and installed version.
- Update the plugin beyond version 3.0.4 if vendor or WordPress guidance provides an available fixed release.
- If updating is not immediately possible, disable or remove the plugin where business impact allows.
- Limit administrator access to trusted users and review accounts with admin privileges.
- Check Wordfence and WordPress plugin guidance for confirmed remediation details.
Validation and detection
- Confirm whether Fathom Analytics plugin version is 3.0.4 or earlier on each WordPress site.
- Review multisite and site settings for environments where unfiltered_html is disabled.
- Inspect plugin configuration values for unexpected script-like content.
- Review recent administrator changes around Fathom Analytics settings.
- Verify remediation by confirming the affected plugin version is no longer present.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-41836 mapping review
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Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N1.72.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.8MediumVector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.wordfence.com/vulnerability-advisories/#CVE-2021-41836CVE reference · x_refsource_MISC
- https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=2641005%40fathom-analytics&new=2641005%40fathom-analytics&sfp_email=&sfph_mail=CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.