Security readout for executives and security teams
Plain-English summary
CVE-2021-4356 affects the WordPress Frontend File Manager plugin up to and including version 18.2. An unauthenticated attacker may be able to download arbitrary site files, which could expose secrets and potentially enable site takeover. Treat exposed WordPress sites using this plugin as high business risk.
Executive priority
Prioritize remediation for public WordPress sites because arbitrary file download can expose database credentials, keys, and private content. Absence from KEV lowers certainty of exploitation, not impact. Patch or remove the plugin promptly and review for compromise if exposed.
Technical view
The issue is missing authentication, capability checks, and sanitization on the wpfm_file_meta_update AJAX action. The CVE maps to CWE-862 and has CVSS 3.1 score 9.0. Source metadata names arbitrary file download with possible confidentiality, integrity, and availability impact; exact fixed version details are not provided in the bundle.
Likely exposure
Internet-facing WordPress sites running the nmedia Frontend File Manager plugin version 18.2 or earlier are the likely exposure. The affected-product metadata in the bundle is incomplete, so teams should verify the exact plugin slug and installed version in WordPress.
Exploitation context
The bundle does not show CISA KEV listing and provides no cited evidence of active exploitation. The vulnerability is unauthenticated and network reachable, but the CVSS vector marks attack complexity high. Do not assume exploitation without log or threat-intelligence confirmation.
Researcher notes
The strongest details are from the CVE description and referenced Wordfence/Nintechnet/WordPress Trac sources. The bundle states versions through 18.2 are vulnerable, but does not provide a clear fixed version. Keep validation focused on inventory, version state, and defensive log review.
Mitigation direction
- Identify all WordPress sites using Frontend File Manager.
- Update the plugin using vendor or WordPress.org guidance.
- Disable or remove the plugin where business use is unnecessary.
- Review site files and secrets for possible exposure.
- Rotate credentials if sensitive configuration files may have been accessed.
Validation and detection
- Confirm whether Frontend File Manager is installed and its version.
- Flag installations at version 18.2 or earlier.
- Review web logs for suspicious unauthenticated admin-ajax.php activity referencing wpfm_file_meta_update.
- Verify the updated plugin enforces authentication and capability checks.
- Check for unexpected admin users, modified files, or exposed backups.
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-862: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. 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 lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-4356 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
- Critical
- CVSS
- 9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
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:H/PR:N/UI:N/S:C/C:H/I:H/A:H2.26Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9CriticalVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.wordfence.com/threat-intel/vulnerabilities/id/79e2011c-5e4d-4d02-831f-6b4dcfcaa51e?source=cveCVE reference
- https://blog.nintechnet.com/wordpress-frontend-file-manager-plugin-fixed-multiple-critical-vulnerabilities/CVE reference
- https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=2554359%40nmedia-user-file-uploader&new=2554359%40nmedia-user-file-uploader&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.
Missing Authorization
Missing Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.