Security readout for executives and security teams
Plain-English summary
CVE-2021-4418 affects the WordPress Custom CSS, JS & PHP plugin through version 2.0.7. If an administrator is tricked into clicking a malicious link while logged in, an attacker could cause code snippets to be saved without proper request validation.
Executive priority
Treat as a moderate WordPress hygiene issue. It is not described as actively exploited, but it can let attackers alter site code if they can socially engineer an administrator.
Technical view
The issue is CWE-352 cross-site request forgery caused by missing or incorrect nonce validation in the plugin's save() function. The reported impact is low integrity compromise: forged snippet changes through an administrator's browser session. The source bundle does not support direct unauthenticated exploitation without user interaction.
Likely exposure
Exposure is limited to WordPress sites running Custom CSS, JS & PHP up to and including 2.0.7, especially where administrators stay logged in while browsing email or external links.
Exploitation context
The CVE is not listed as KEV, and the provided sources do not state active exploitation. Exploitation requires administrator interaction, such as clicking a crafted link, and depends on the vulnerable plugin being installed and active.
Researcher notes
The strongest evidence is the CVE description and Wordfence-style advisory data identifying missing nonce validation in save(). The affected-version metadata is inconsistent in the bundle, so prioritize the prose statement: vulnerable through 2.0.7.
Mitigation direction
- Inventory WordPress sites for Custom CSS, JS & PHP versions through 2.0.7.
- Update to a vendor-supported non-vulnerable version if available.
- Disable or remove the plugin where updates are unavailable or unnecessary.
- Restrict WordPress administrator access to trusted users only.
- Warn administrators not to click untrusted links while logged in.
Validation and detection
- Confirm whether each WordPress site has the affected plugin installed and active.
- Check plugin version and flag versions up to and including 2.0.7.
- Review saved CSS, JavaScript, and PHP snippets for unexpected changes.
- Review administrative activity logs for unusual snippet saves.
- Confirm the current plugin version uses proper nonce validation for save actions.
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-2021-4418 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/d21dc02f-789c-497e-9d01-02fa49bf9e30?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/browser/custom-css-js-php/trunk/modules/code/model.code.php#L85CVE 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.
Cross-Site Request Forgery (CSRF)
Cross-Site Request Forgery (CSRF) represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.