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Fencer Intel
medium 4.3

CVE-2021-4418 json

Custom CSS, JS & PHP <= 2.0.7 - Cross-Site Request Forgery Bypass

published 3y ago modified 4mo ago also EUVD-2021-34245

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

The Custom CSS, JS & PHP plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 2.0.7. This is due to missing or incorrect nonce validation on the save() function. This makes it possible for unauthenticated attackers to save code snippets via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.

Patch / fix

Is CVE-2021-4418 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2y ago

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • blog.nintechnet.com https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-2/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Affected products

  • flippercode Custom css-js-php

Classification

Weakness
  • CWE-352 Cross-Site Request Forgery
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.