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CVE-2021-39318

21
FAUCET Score

CVE-2021-39318 describes a Reflected Cross-Site Scripting (XSS) vulnerability in the H5P CSS Editor WordPress plugin, affecting versions up to and including 1.0. An unauthenticated attacker can exploit this by injecting arbitrary web scripts through the 'h5p-css-file' parameter in 'h5p-css-editor.php'. With a CVSS score of 6.1 (Medium), this vulnerability requires user interaction (UI:R) but has low attack complexity (AC:L), potentially leading to limited impact on confidentiality and integrity (C:L/I:L). There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 1.0CPE matchmatch criteria
cpe:2.3:a:h5p-css-editor_project:h5p-css-editor:*:*:*:*:*:wordpress:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.76%
Probability of exploitation in next 30 days
EPSS Percentile
51.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0076 is in the 58th percentile among its peer group of 26,234 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

plugins.trac.wordpress.org / browser/h5p-css-editor/tags/1.0/h5p-css-editor.php
Third Party Advisory
wordfence.com / vulnerability-advisories
Third Party Advisory