Security readout for executives and security teams
Plain-English summary
This affects WordPress sites running the Remove Schema plugin through version 1.5. A malicious link or page could make an authenticated administrator unknowingly submit a settings change. It does not indicate direct server takeover, but it can alter plugin behavior and create integrity risk.
Executive priority
Treat as a moderate WordPress hygiene issue. Prioritize public or business-critical WordPress sites, especially where administrators routinely access email or third-party pages while logged in.
Technical view
CVE-2021-4403 is a CSRF issue caused by missing or incorrect nonce validation in the plugin's validate() function. The published impact is unauthorized modification of plugin settings when an administrator is tricked into performing an action. CVSS 3.1 is 4.3, with low integrity impact and required user interaction.
Likely exposure
Exposure is limited to WordPress installations using Remove Schema versions up to and including 1.5. Sites not using this plugin are not exposed based on the provided sources.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. Exploitation requires social engineering an authenticated site administrator into triggering a forged request.
Researcher notes
The key evidence is CSRF through missing or incorrect nonce validation in validate(). The bundle supports settings modification impact only; it does not support remote code execution, data theft, or active exploitation claims.
Mitigation direction
- Inventory WordPress sites for the Remove Schema plugin and version.
- Update to a vendor-fixed release if available from trusted plugin sources.
- Disable or remove the plugin where updates are unavailable or unnecessary.
- Review plugin settings for unexpected changes after suspected exposure.
- Monitor vendor and WordPress plugin repository guidance for exact fixed-version details.
Validation and detection
- Confirm whether Remove Schema is installed on each WordPress property.
- Verify installed versions are newer than 1.5 or otherwise vendor-fixed.
- Review administrative logs for unexpected plugin settings changes.
- Check source changes for nonce validation around the validate() function.
- Confirm administrator workflows do not rely on untrusted links for settings changes.
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-352: 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-2021-4403 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/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:N/UI:R/S:U/C:N/I:L/A:N2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.wordfence.com/threat-intel/vulnerabilities/id/89635463-966d-4f7d-995d-ad83a502d95b?source=cveCVE reference
- https://blog.nintechnet.com/25-wordpress-plugins-vulnerable-to-csrf-attacks/CVE reference
- https://blog.nintechnet.com/more-wordpress-plugins-and-themes-vulnerable-to-csrf-attacks/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-3/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-2/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-1/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-5/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-4/CVE reference
- https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=2548575%40remove-schema&new=2548575%40remove-schema&sfp_email=&sfph_mail=CVE reference
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.